Grand Coulee is a city in Grant County, Washington, United States. The population was 988 at the 2010 census. Take a look below for 15 awesome and fascinating facts about Grand Coulee, Washington, United States. 1. Grand Coulee is located at 47°56′23″N 119°0′6″W (47.939706, -119.001597). 2. According to the United States Census Bureau, the city…