Grant County is a county located in the U.S. state of Washington. As of the 2010 census, the population was 89,120. The county seat is Ephrata and the largest city is Moses Lake. The county was named after U.S. President Ulysses S. Grant.
Grant County was formed out of Douglas County on February 24, 1909.
- Founded: February 24, 1909
- Seat: Ephrata
- Largest City: Moses Lake
- Total: 2,791 square miles (7,229 square kilometers)
- Land: 2,681 square miles (6,944 square kilometers)
- Water: 110 square miles (285 square kilometers), 3.95%
- Population Estimate (2011): 91,265
- Density: 33 per square mile (12.8 per square kilometer)
- Time Zone: Pacific - UTC-8/-7