The seat of Richland County
, Sidney is located 41 miles northeast of Glendive
near the North Dakota state line on Hwys 200/16 on the banks of the Yellowstone River
. It is home to the MonDak Heritage Center Musseum, which features extensive exhibits of area histroy, art exhibits and a research library.
The population estimate for July 1, 1998 was 4,865, a decrease of 352 since 1990.