Skip to main content

Star Gazers' Stone - Chester County, Pennsylvania


One of the most important surveying markers in the United States, and perhaps, the world, is located in an otherwise unassuming field at Embreeville in Newlin Township in Chester County, Pennsylvania. That marker is the Star Gazers' Stone, which is the land marker that was used in 1764 by 18th century astronomers Charles Mason and Jeremiah Dixon to determine the true boundary between Pennsylvania and Maryland.

At the time, the colonies of Maryland and Pennsylvania had a disputed border thanks to competing royal charters of the time. Maryland and Pennsylvania both claimed the land between the 39th and 40th parallels according to the charters granted to each colony, and this would have included the City of Philadelphia. The issue was unresolved until the British Crown intervened in 1760, ordering Frederick Calvert, 6th Baron Baltimore to accept a border agreement signed in 1732. As part of the settlement, the Penns and Calverts commissioned the team of English astronomers Charles Mason and Jeremiah Dixon to survey the proper boundaries between Pennsylvania, Maryland, Delaware and parts of Virginia.

The Mason-Dixon Line (the northern boundary of Maryland) was to be 15 miles south of the southernmost house in Philadelphia. On January 7, 1764, after finding the latitude of the house, they picked out a location 31 miles west of Philadelphia at John Harlan's farm in modern day Embreeville, Pennsylvania at the same latitude of the forks of the Brandywine Creek. Moving their delicate but heavy equipment took two days. They moved westward because surveying 15 miles directly south from Philadelphia would have involved a difficult crossing of the Delaware and would have landed them in New Jersey from which they would have to cross the Delaware again on the way west. It made more sense for Mason and Dixon to set up their base of operations for astronomical observations to the west of Philadelphia. A reference point in the garden of the Harlan property, now known as Star Gazers' Stone, was placed to mark the astronomical meridian line north of their observatory.

Using a device with a 6 foot long brass telescope that allowed them to establish their position relative to the stars, Mason and Dixon spent the winter nights charting the sky from the Star Gazers' Stone. In spring 1764, they ventured due south from the farm with a team that cleared a wide swath through the dense forests. Using chains and levels, they surveyed in straight, 12 mile segments, then made detailed astronomical calculations to adjust to the exact latitude. As miles were measured differently in the 18th century, the majority of the original stones were not actually placed a mile apart by today's standards. While many of the 230 original crown stones have been lost over time, the Stargazers’ Stone, the starting point of the boundary survey, is located in exactly the right place.

Today, you can visit the Star Gazers' Stone by taking a short hike in the ChesLen Preserve off of PA 162 in Embreeville, near the intersection with the aptly named Stargazers Road. There is a parking lot and a trail that leads to the Star Gazers' Stone, along an easement surrounded by a privately owned property. I enjoyed this short journey to this widely overlooked, but very important piece of our history.

Along the trail to the Star Gazers' Stone

Star Gazers' Stone historical plaque.

Star Gazers' Stone keystone marker located on Stargazers Road.

The Star Gazers; Stone is protected by a stone encasement.

How to Get There:

Sources and Links:
Landmarks - The Star-Gazers' Stone
Historical Marker Database - The Star Gazers' Stone
Natural Lands - Star Gazers’ Stone More Accessible to Visitors
Town of Rising Sun, Maryland - History of the Mason-Dixon Line
Scott's ODDySEEy (YouTube) - Stargazers Stone | A Line Drawn in the Sand...stone
Vista.Today - Most Important Stone Along Mason-Dixon Line Has Survived Centuries in Newlin Township

Crossposted to Quintessential Pennsylvania -


Popular posts from this blog

Dillon Road

Dillon Road is a 34.2-mile highway located in northern Coachella Valley of Riverside County, California.  Dillon Road begins at Avenue 48 on the outskirts of Indio and ends to the west at California State Route 62 near San Gorgonio Pass.  Dillon Road was developed the 1930s as a construction road for the Colorado River Aqueduct.  Dillon Road serves as a northern bypass to much of the development of Coachella Valley.  Dillon Road is known for it's frequent dips and spectacular views of San Gorgonio Pass.   Part 1; the history of Dillon Road Dillon Road was constructed as a haul road for the Colorado River Aqueduct through Coachella Valley.  The Colorado River Aqueduct spans 242 miles from Parker Dam on the Colorado River west to Lake Mathews near Corona.  Construction of the Colorado River Aqueduct began during January 1933 near Thousand Palms and was made functional on January 7, 1939.  West of Berdoo Canyon Road the alignment of Dillon Road is largely concurrent with the Colorado

Tehachapi-Willow Springs Road

Tehachapi-Willow Springs Road is an approximately 21-mile highway located in southeast Kern County.  Tehachapi-Willow Springs Road begins at Tehachapi Boulevard (former US Route 466) in Tehachapi and crosses the Tehachapi Mountains via the 4,820-foot-high Oak Creek Pass.  Tehachapi-Willow Springs Road enters Antelope Valley of the wider Mojave Desert and passes by the historic stage station of Willow Springs to a southern terminus at Rosamond Boulevard.  Tehachapi-Willow Springs Road has historic ties to the Havilah-Los Angeles Road and Stockton-Los Angeles Road due to the once reliable presence of water at Willow Springs. Part 1; the history of Tehachapi-Willow Springs Road Oak Creek Pass and Willow Springs were known to the local tribes of the Tehachapi Mountains for generations.  The first documented European crossing of Oak Creek Pass was during 1776 as part of an expedition by Francisco Garces.  Oak Creek Pass is as used again by John C. Fremont during an 1844-1845 expedition to e

The 1928 Iowa Hill Road Bridge

The 1928 Iowa Hill Road Bridge is a derelict structure located in the Sierra Nevada Mountains of Placer County, California.  The 1928 Iowa Hill Road Bridge can be found between the communities of Colfax and Iowa Hill.  The 1928 Iowa Hill Road Bridge is a wire suspension structure which spans the North Fork American River.  The 1928 Iowa Hill Road Bridge was replaced by a modern span and converted to pedestrian use following floods during 1963.   Part 1; the history of the 1928 Iowa Hill Road Bridge During 1853 gold was discovered at what to become Iowa Hill.  The gold mining claims soon led to a small community known as Iowa City being established.   By 1854, Post Office Service began at the mines of Iowa City.  By 1856 gold production at Iowa City was estimated to be around $100,000.  Iowa City was burned in fires during 1857 and 1862 but the community was rebuilt with more modernized structures.   The location of Iowa City can be seen as "Iowa Hill" on the 1873 Bancroft