The Initial Point for Montana is on a fairly unremarkable hill in the southwestern part of the state, ten miles southwest of the headwaters of the Missouri River. The Surveyor General of the territory had imagined it being placed on a prominent landmark on the river known as Beaverhead Rock, but the surveyor in the field deemed it unsuitable and settled on this site instead. For some reason it was never given an official name, so Montana’s meridian is referred to descriptively as Principal Meridian, Montana. It was set in 1867, and is still marked by the three-inch brass cap placed there in 1922 by the U.S. Land Office. The site is surrounded by a private ranch.
All of Montana was measured from this nameless Initial Point.
The intersection of the baseline and meridian at the Initial Point for Montana, located in the center of the map, and the Jefferson River, which flows into the headwaters of the Missouri River, upper left.