Lancaster is a city in Dallas County, Texas, United States. The population was 36,361 at the 2010 census. Lancaster is a suburb of Dallas and is part of the Best Southwest area, which includes Lancaster, Cedar Hill, DeSoto, and Duncanville. Most of the city is in Dallas County, but a small southern section spills over into Ellis County. All of the Ellis County section of Lancaster is plain land with only a few houses and roads in the southern section of the city. On April 3rd 2012, an EF-2 tornado struck the city as part of the April 3, 2012 tornado outbreak. 300 structures were reported damaged. A tornado emergency was not called for Lancaster, but a tornado emergency was called for the nearby cities of Dallas, Greenville, and Arlington. No deaths were reported from either the Lancaster tornado or any other tornado that day.