Volunteer surveyors establish the location of the State House Observatory where the Declaration of Independence was first read to the public.

The gray weathered steps creaked beneath his feet as he ascended to the balcony of the wooden structure. Col. John Nixon, commander of the Philadelphia city guard, held in his hands a large, rolled parchment. He had read it through several times and was well aware of the impact it would have on his life and the lives of his fellow citizens. The document had recently been printed and copies were already on their way to every colony in America.

Now, on July 8, 1776, the city of Philadelphia was pulsating with energy. In the latter part of this summer Monday morning, church bells and the State House bell had tolled to call the people together. The citizens of the city, her merchants, bakers, bankers and children, had responded to this call and waited expectantly for the public reading of the proclamation.

Col. Nixon had been selected by Philadelphia's sheriff, William Dewees, to address the crowd called to the State House yard. The balcony upon which he stood was an ideal location to make public announcements. From his perspective, Col. Nixon found it to be a wonderful vantage point to observe the gathered crowd. Also joining him on the balcony were members of Pennsylvania's Committee of Safety, which was charged with the defense of the colony, and local dignitaries. The bells ceased tolling and the multitude was called to silence. Col. Nixon, in a loud and resonant voice, began to read:

When, in the Course of human Events, it becomes necessary for one People to dissolve the Political Bands which have connected them with another, and to assume among the Powers of the Earth, the separate & equal Station to which the Laws of Nature and of Nature's God entitle them, a decent Respect to the Opinions of Mankind requires that they should declare the causes which impel them to the Separation."

And so began the first public reading of The Declaration of Independence.

Surveying at the intersection of South and Front Streets in Philadelphia to establish the "Southernmost Point in Philadelphia."

Setting the Stage

Much has been written about the events that took place at the State House during the summer of 1776. This home of Colonial Pennsylvania's government later became known as Independence Hall for the momentous proceedings that occurred there. It was in the State House in June 1776 that Richard Henry Lee introduced a resolution that "these United Colonies are, and of right ought to be, free and independent States."

This ultimately lead to the adoption of the Declaration of Independence in the State House on July 4, 1776. A good deal is known about the men who mutually pledged to each other their lives, fortunes and their sacred honor on this occasion. Little, however, is known about the edifice from which Col. Nixon first proclaimed liberty to the inhabitants of the city of Philadelphia and consequently the world. The words spoken from "that awfull Stage in the State house Yard" as John Adams described it,1 still resonate around the world.

The route of William Smith's 1769 survey drawn on a Pennsylvania Department of Transportation map.

Origins of the Observatory

The balcony from which the Declaration of Independence was first publicly read was part of an observatory constructed in 1769 by the American Philosophical Society to observe the Transit of Venus, a rare astronomical event where the planet Venus passes between the Earth and the sun. An occurrence of the Transit of Venus was observed in 1761, and its recurrence in 1769 provided another opportunity for the advancement of scientific knowledge.

The American Philosophical Society wanted to leap upon the scientific world stage and made plans to sponsor observations of the transit at various locations throughout the colonies. The preeminent David Rittenhouse, colonial clockmaker, instrument maker and surveyor, observed the transit from his home-based observatory at Norriton near present-day Valley Forge, Pa. Surveyors Owen Biddle and Joel Bayley were dispatched to Lewes (Lewestown), Del. at the mouth of the Delaware Bay to observe the transit in that small shorefront community. And the society built the State House Observatory so Reverend John Ewing, Joseph Shippen, Dr. Hugh Williamson, James Pearson and Thomas Prior could perform observations in Philadelphia.

In addition to its scientific role, we also know of the observatory's political significance because a number of personal accounts record that the Declaration was read in the State House yard, which is the area south of Independence Hall where the observatory was located. Following the first public proclamation of the Declaration of Independence on July 8, 1776, little mention has been made of the observatory constructed in the State House yard. During the Revolution it was enclosed and housed British soldiers during the occupation of Philadelphia in 1777. It was little used after the Revolutionary War and soon fell into disrepair. There has been much speculation over the years regarding its location and several archaeological excavations have been made to uncover evidence about the original location of the observatory. The key to this mystery was uncovered in a volume of papers published by the American Philosophical Society in 1771.

Finding the Key

In February 2003, I was called to Philadelphia to serve on federal jury duty. On my last day in Philadelphia, I was released from service early in the day, which gave me some unexpected spare time. I decided to call on Roy Goodman, an acquaintance of mine who works as the reference librarian at the American Philosophical Society. At the time, I was searching for records of astronomical observations that were made from the State House Observatory in the hope that these measurements might provide some insight as to its location. I had been curious about the location of the observatory for about 10 years-ever since I had read an essay by Silvio Bedini titled "That Awful Stage, the Search for the State House Observatory."2

While scanning the index of the papers contained in the society's transactions,3 I noticed a reference to a paper by William Smith titled "Account of the terrestrial measurement in the difference in Longitude and Latitude between the observatories of Norriton and Philadel-phia." Upon review of the paper, I found it contained the results of a compass and chain survey between the Rittenhouse Observatory, the State House Observatory and the point established as the "Southernmost Point in Philadelphia" during the Mason-Dixon boundary survey of Pennsylvania and Maryland. This survey was performed in 1769 at the request of Astronomer Royal Nevil Maskelyne to calculate the relative positions of the three observatories in Colonial America from which the Transit of Venus had been observed.

The ride home from Philadelphia that day was a blur. I realized that this survey was the key to actually calculating the position where the State House observatory had once stood and determining the very spot where the Declaration of Independence was first publicly proclaimed.

Surveying in the area south of Independence Hall where the State House Observatory would have been located.

The Terrestrial Survey between the Observatories of Norriton and Philadelphia

For some time, I had thought it might be possible to calculate the position of the State House Observatory from the astronomical observations performed during the years the observatory was used. I thought that perhaps the records of the American Philosophical Society would contain sufficient solar or astronomical observations to calculate the position. Many previous researchers and physical searches for the observatory had focused on an area close to the American Philosophical Hall and about 50 ft south of Independence Hall. If the observatory had been located that close to the buildings, the astronomical observations might have reflected areas where the buildings obstructed the sky.

With the discovery of the 1769 survey, I now had a new direction to pursue to establish the location of the observatory. Initially, I plotted the 1769 survey on vellum paper and overlaid it on a USGS quadrangle map. The course of the survey ran from the Rittenhouse homestead and followed Germantown Avenue, Ridge Pike and Sixth Street to the State House Yard, and subsequently to the position established as "the southernmost point in Philadelphia." By establishing the fixed location of this southernmost point, the survey could be rotated to align with the roads between Philadelphia and the Observatory at Norriton under the assumption that the general course of these roads had not changed much over 230 years. The entire traverse covers a distance of 21 miles from the Rittenhouse Observatory to the southernmost point of Philadelphia. If the location of the Rittenhouse Observatory could be established to within 100 ft, the calculated location of the State House Observatory should not be in error by more than 4 ft.

One interesting discovery was that despite William Smith's assertion that he and Jesse Lukens and Archibald McClean independently made the calculations, there are still two errors in the computations. The first error is rather insignificant and is found in the 46th course of the survey. Two numbers were transposed in the westing column and should have read 2.4310 chains (versus 2.4301 chains), resulting in a difference of only three-fourths of an inch. The second error is more significant, and I find it surprising that three competent men did not notice the discrepancy. The 69th and final course from Sixth Street to the State House Observatory should have had an easting of 1.7441 chains (versus 1.7741 chains). This is a difference of .03 chains or 1.98 feet, an error that was carried through the remainder of the calculations. For the purpose of this survey, I have assumed that the recorded value of South 77 East - 1.79 chains is correct and the other values were adjusted accordingly.

Setting GPS base control in the mall area north of Independence Hall.

The Mason and Dixon Connection

After many years of debate, dispute and court proceedings, a resolution was finally reached that established the boundary between Pennsylvania and Maryland. The boundary decided upon was established as a line of latitude 15 miles south of the "southernmost point in Philadelphia." In 1763, Charles Mason, Jeremiah Dixon and the commissioners appointed to oversee the survey of the boundary between Pennsylvania and Maryland met with the mayor and aldermen of Philadelphia and agreed upon the north wall of a house located on the south side of Cedar (South) Street. The location of this house has been widely accepted as the Plumstead and Huddle house located at 30 South Street. This house was destroyed by the construction of Interstate 95 in the 1960s.

To re-establish the location of the Plumstead and Huddle house, I performed a field survey in April 2004 to locate the existing buildings, party walls and curb lines at the intersection of South and Front Streets. Using plans supplied by James Shomper, a now retired Philadelphia City Regulator, I was able to re-create the location of the house that once stood at 30 South Street.

Records do not clarify where Mason and Dixon measured on the front of the house. For the purpose of this project, it was assumed that they measured from the center of the dwelling front. Although the eastern corner would actually have been farther south, I do not believe they used the eastern corner. If the eastern corner of the dwelling were to have been used, the survey ties Mason and Dixon made to their observatory location would have fallen within Front Street. However, this is contrary to Mason's field notes, which indicate the meridian line from the observatory intersected with the south side of Cedar (South) Street. Therefore, I safely assumed that the southernmost point of Philadelphia was the center of the north wall of the house located at 30 South Street.

The "Colonial Foot"

Philadelphia has the distinction of a measurement anomaly surveyors refer to as the "Philadelphia foot." Each district of the city has a differing standard for the length of the foot. On average, three inches must be added per 100 feet to compare with the street and block distances. This is a carryover from colonial days when the length of a "foot" had not yet evolved into what we consider the standard U.S. Survey foot.

In my work on the recovery of the stones marking the Mason and Dixon Line, I have found the distance between the stones averages to be 5,295 to 5,300 ft. The stones were to have been set at one-mile intervals, but we find that they are 15-20 feet long between stones, or about 3 1⁄2 to 4 1⁄2 inches long per 100 feet. The boundary of Washington, D.C., was surveyed in the 1790s and is supposed to be 10 miles square. Modern day measurements find that the length of the sides is long by 3 1⁄2 inches per 100 feet. This is not to say that the surveyors were wrong. Skilled men using the most modern equipment available performed each of the surveys with great care. It is my belief that it should not be referred to as the Philadelphia foot, but rather the "colonial foot."

With this in mind, I first looked at the traverse using the original distances recorded by the surveyors. I found that this would place the Rittenhouse Observatory too far east of his homestead, placing it across a stream on a slope. This is not a very likely location for the observatory. I next scaled the survey adding three inches per 100 feet to conform more closely with what I believe would have been the length of their foot, but the observatory still fell too far east of his house and in the stream valley. I then scaled the traverse adding four inches per 100 feet, which seems a bit much, but it places the observatory slightly to the west and north of Rittenhouse's homestead in an area that would be conducive to the construction of an observatory.

The Rittenhouse Observatory

The Rittenhouse Observatory was constructed in the spring of 1769 in anticipation of the Transit of Venus. The current owners of the property were under the impression that the observatory was constructed across a small stream and on top of a hill some 300 to 400 feet south and west of the Rittenhouse home. This location would seem logical considering the excellent view of the sky from that location. But I found that this would place the observatory far too close to the road, owing to the distances recorded in the 1769 survey. In addition, in a letter from David Rittenhouse to the Reverend Dr. Ewing, Rittenhouse notes that from his observatory, he established a meridian mark to the north that was later obstructed by the construction of a brick building. He also notes that buildings obstructed his view to the south. (We could guess that this was probably his house or other outbuildings.) He later notes that he established a meridian mark by screwing "fast a piece of brass to a block of marble, supported by a brick pillar built on a good foundation, for this purpose, in my garden." Certainly his garden would not have been located several hundred feet away from his house, across a stream and up a hill! It would likely have been located behind his house on the level area.

Looking south along Sixth Street in the direction of Independence Hall along the path taken by the 1769 surveyors.

Following in their Footsteps

In April 2004, I received permission from the National Park Service (NPS) to perform a survey in the area of Independence Hall. In the wake of September 11th, security in the area was very restrictive. We met with Robert Giannini, NPS museum curator at Independence Hall, who graciously escorted us through the web of security, assuring the multitude of armed guards that "these guys carrying the tripods, rods and boxes are harmless." My son Craig, Rev. David Rowe, Dale Aulthouse and Fred Achenbach helped carry equipment and stay with the instruments when we had to move around the site.

Control points established near the intersection of South and Front Streets were connected to those set in the mall area near Independence Hall using two Ashtech (Thales, Santa Clara, Calif.) Z-Max GPS units. From this base control, I then used a Leica Geosystems (Norcross, Ga.) TCRA 1101+ reflectorless robotic total station to set supplemental control and to locate ground features, curblines, buildings and trees.

I processed the data and established coordinates for the base points using the National Geodetic Survey's OPUS (Online Positioning User Service), then imported the survey points into Trimble (Sunnyvale, Calif.) Terramodel software. I also imported parcel, curb and cartway edge Shape files from the Philadelphia GIS system into my base drawing, after first viewing the files in ESRI (Redlands, Calif.) ArcExplorer. The traverse information from the 1769 survey between the three observatories was plotted and overlaid to see how well the three points fit together. I also imported AutoCAD files (Autodesk, San Rafael, Calif.) provided by an archaeologist for the NPS that contained the locations of past archaeological excavations and old parcel lines.

After analyzing several scenarios, I narrowed the possible location of the State House Observatory to an area roughly 12' x 20'. Interestingly, this area was approximately 230 feet south of Independence Hall and on the west side of the State House Yard, placing it much farther south and west than previously thought. The most important finding, in my opinion, was that this also placed the observatory south of a wall that had been constructed between 1740-42 that was still in place in 1769 when the observatory was constructed.

This is a critical point for two reasons. First, in 1736 there was an ordinance passed that prohibited the construction of any buildings in the State House Yard. It would therefore make sense that the observatory constructed by the American Philosophical Society would have been constructed outside of the original wall. The wall was destroyed later in 1769 when the yard was extended south to Walnut Street. Secondly, it makes clear the reason the observatory was constructed as an elevated platform. In order to make the observations, it would have been necessary to elevate the observatory platform above the height of the wall enclosing the State House Yard. Normally, an observatory would be constructed on the ground to avoid vibration of the instruments caused by the movement of observers. A description of the observatory construction notes that special care was made during the construction of the State House Observatory to stabilize the center post upon which the timepiece would be affixed and create a separate platform upon which the observers could stand.

In June 2004, an opportunity arose to conduct a limited archaeological excavation in the area where I had calculated the observatory once stood. The slate sidewalk in the area was in need of repair and the NPS seized the opportunity to conduct an excavation. I returned to Independence Hall with my son Craig and a fellow surveyor, William Coller, PLS, to mark the position where I had calculated for the position of the observatory. Looming thunderstorms threatened to cut short our return trip to Philadelphia. Using the previously established control points, Bill and I placed reference points for the archaeologists to use during their excavation. Fortunately, the storms held off long enough for us to mark the points and also locate some additional trees and walkways in the area for future reference.

Subsequently, a team of archaeologists from John Milner Associates (West Chester, Pa.) directed by Dr. Rebecca Yamin excavated a trench in the area. The trench revealed a "pit feature" that contained a large quantity of oxidized nails, a handle, small fragments of ceramics, glass, bone and shell. The artifacts must be cleaned and catalogued, but they tentatively date between 1755-1775 and none of the findings appear to post-date the Revolution. While this is not in itself proof that this location is the site of the observatory, the findings are evidence of significant activity around the time the observatory was in use.

Hopefully, an opportunity will arise in the future for a more extensive excavation to uncover additional evidence of the location of the observatory where liberty was first publicly proclaimed throughout the land on July 8, 1776.