sidneySidney is a city in and the county seat of Richland County, Montana, United States, [4] less than 10 mi (16 km) west of the North Dakota border. The population was 6,346 at the 2020 census.SIDNEY — The Lehman Catholic Cavaliers took a 4-1 victory over the Mississinawa Valley Blackhawks on Thursday at Lehman Hh School in a Division VII District