Where the Central and Mountain time zone line runs

Mountain Time begins west of the line described in 49 CFR 71.7. From the Canadian border the line follows the Montana–North Dakota line, then the Missouri and Yellowstone rivers, then county and highway lines through western North Dakota. South Dakota uses the Missouri until a point near Pierre, then county lines so Jones, Mellette, and Todd stay central while the west-river counties are mountain.

Nebraska's boundary is the most intricate on the map: it steps along range and section lines through the Sandhills before it settles onto county lines near the Colorado line. Cherry County is one of the counties the description cuts through, and the sample agrees that it is split.

Kansas is simpler. Sherman, Wallace, Greeley, and Hamilton counties are Mountain Time. Every other Kansas county is Central. In Texas, only El Paso and Hudspeth counties are Mountain; the line is Hudspeth's eastern border down to Mexico. A town sitting on this central–mountain line is legally Mountain Time, except Murdo, South Dakota, which 49 CFR 71.7(g) keeps on Central Time.