Sponsored Topics. Santa Clara is a city in Washington County, Utah, United States. The population was 4,630 at the 2000 census. According to the United States Census Bureau, the city has a total area of 4.9 square miles (12.7 km²), of which, 4.9 square miles (12.6 km²) of it is land and 0.04 square miles (0.1 km²) of it (0.41%) is water.