Which Nebraska Counties Are in Mountain Time?
Eighteen Nebraska counties are entirely in Mountain Time: Arthur, Banner, Box Butte, Chase, Cheyenne, Dawes, Deuel, Dundy, Garden, Grant, Hooker, Keith, Kimball, Morrill, Perkins, Scotts Bluff, Sheridan and Sioux. The western part of Cherry County is also in Mountain Time.
PanhandleBanner, Box Butte, Cheyenne, Dawes, Deuel, Garden, Kimball, Morrill, Scotts Bluff, Sheridan and Sioux are Mountain Time.
Additional western countiesArthur, Chase, Dundy, Grant, Hooker, Keith and Perkins are Mountain Time.
Cherry County exceptionWestern Cherry County is Mountain Time; eastern Cherry County is Central Time.
Where Does the Time Zone Change in Nebraska?
The legal boundary is defined in 49 CFR §71.7(c). From the South Dakota line it follows survey range, township and section lines through north-central Nebraska, then county boundaries involving Thomas, McPherson, Keith, Lincoln, Hayes and Hitchcock counties before reaching Kansas.
The result is a jagged boundary rather than a clean vertical line. That explains why North Platte remains in Central Time while Ogallala in Keith County is in Mountain Time, and why Cherry County is split. Under §71.7(g), municipalities located directly on the boundary are assigned to the Mountain Standard Time zone.