Isaac Roop was the first provisional governor of the territory of Nevada.

Roop's Fort is a log structure with one floor and a loft and no foundation. At thirty feet by twenty-one feet, it is large for a log building. It is located on its original site. A repaired shake roof is the only alteration.

Roop's Fort was the first building erected in Lassen County by a pioneer. It was the first trading post the emigrants encountered after Fort Hall in Idaho on their way west.

Roop's Fort was called Fort Defiance during the Sagebrush War between Lassen County and Plumas County.

Source: Adapted from the NRHP nomination submitted in 1974.