Garfield County was founded in 1882 and was named for U.S. President James A. Garfield who had been assassinated just a year earlier.

The county has a total area of 5,208 square miles, of which 5,175 square miles is land and 33 square miles is water. The Colorado River, passing through a deep gorge, forms the eastern boundary. Westward, the cliffs of tributary canyons give way to the barren stretches of the San Rafael Desert, beyond which a variety of mountains, plateaus and canyons make up the terrain.

Most of Bryce Canyon National Park lies in the southwestern part of the county and the northern half of the Grand Staircase-Escalante National Monument occupies the middle of the county. A large portion of Capitol Reef National Park lies in the east-central part of the county. A very small part of Canyonlands National Park lies in the northeast corner of the county.