Santa Clara (Washington) is on the Santa Clara River just northwest of St. George. In 1854 Jacob Hamblin established an Indian mission here. A few years later, 1856, a fort was built. In 1861 fifteen Swiss families arrived to settle here. However, as happened so often in the southwestern part of Utah, in 1862 the settlement was wiped out by floodwaters, then rebuilt on higher ground. These settlers planted fruit trees, vineyards, and vegetables which flurished and were in sufficient abundance to be sold in utah and Nevada.
Flooding, 2005, 2010, remains a problem for the Santa Clara area. The river's banks have been shored up substantially with riprap to help control the annual sometimes heavy snow run-off out of the nearby mountainous Pine Valley area. Signal Peak, Washington county's highest point at 10k+ feet in elevation, is just 23.2 miles (37.33 km) north of Santa Clara.
The name of the river originated with travelers on the Old Spanish Trail who trekked along the river. Impressed by the consistently clear weather in the region, named it the Santa Clara.
G. William Wiersdorf
See: Utah Place Names, John W. Van Cott; Santa Clara Historical Society.