Sunnyvale is a rural, sparsely populated, town in Dallas County, Texas, United States. It is the easternmost city completely within Dallas County. The population was 5,130 at the 2010 census.
The town now called Sunnyvale was inhabited by various Native American tribes in the years before the European conquest of the Americas. It became under the rule of Spain in the 18th century, very close to the boundary of Spanish and Frenchterritory (although this boundary was carried upward a bit in 1819; see Adams-Onís Treaty.) During this time, the area was relatively underdeveloped. However, some settlers migrated to Texas and would eventually settle in Sunnyvale.