Congress defined the eastern boundary of Calfornia to include a diagonal line roughly parallel to the Sierra Nevada range. Specifically, the line defined runs southeastward from the point 39°N 120°W to another point where the 35°N latitude line crosses the Colorado River.
The first of those two points happens to be located in the middle of Lake Tahoe. The second point, by definition, is also located within water!
These facts, the fact that both end points were located in water and the challenges associated with surveyiing diagonal lines using 19th century equipment and techniques, mean that no official survey of california's border was conducted for more than two decades after the Golden State achieved statehood in 1850.
In 1872, the engineer Alexey Von Schmidt was tasked with organizing a survey party to undertake the task, surveying a diagonal line which traversed 400 miles of mostly inhospitable territory, with terrain consisting almost entirely of mountains and valleys with a little desert topography mixed in. As the party completed its survey and arrived at the right bank of the Colorado River. They planted the survey marker which can be found today along the Needles-Laughlin Highway, just west of the Avi Tribal Casino.
Modern surveying inform us that the marker is not located directly on the the border between California and Nevada, but is instead completely within California, about 1200 meters (3/4 mile) away from border. Not bad for a survey team which had just completed measurements over 650 km (400 miles) using hundreds of hypotenuse calculations in the era before electronic calculators. Their error margin was less than 2/10 of 1%.
©2023-25 Dan Stober
Created 2023-04-22
Updated 2025-04-02