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 is located on the southern tip of Vancouver Island on the Saanich Peninsula – just a 20 minute drive from downtown Victoria. Sidney is home to the Sidney Anacortes Ferry Terminal