https://en.wikipedia.org/wiki/Washington_meridians

  The Washington meridians are four meridians that were used as prime meridians in the United States which pass through Washington, D.C.

This is the source of my favorite border dispute.

https://en.wikipedia.org/wiki/Lake_Tahoe#Interstate_boundary...

In summary there is a border dispute between California and Nevada, It was exacerbated by some surveying errors but the real problem appears to be the definitions of the sate borders, California was defined using one method(120 degrees longitude west of Greenwich) and Nevada was defined using another method (37 degrees longitude west of Washington) at the time it was thought these two methods were equivalent but it later turned out they are not. Congress does not have the authority to change state borders so it is up to the states to reach an agreement. and they have not. So the dispute is still technically on going.

Researching this also lead to the most hilarious passive aggressive thing I have seen in a constitution.

"All territory lying West of and adjoining the boundary line herein prescribed, which the State of California may relinquish to the Territory or State of Nevada, shall thereupon be embraced within and constitute a part of this State."

We really wanted that area east of the Sierra Nevada mountains, they would form a perfect natural boundary, but CA has already claimed it. If CA ever wants to give it up we want to make sure it is explicitly in the constitution to accept it.

Don't give Trump any ideas.