Tharp was born in Michigan in 1828. In 1851, a widow from Illinois, Chloe Ann Smith Swanson, hired Tharp to take her and her four sons to California in a covered wagon with two teams of oxen. They settled in Placerville, where Tharp married Swanson. Tharp then began mining in California’s Gold Country.
In the summer of 1856, Tharp went to Tulare County to establish a preemption homestead, with the intent to return later to ranch cattle. He built a shake and brush shack near the confluence of the Kaweah River and Horse Creek, east of Visalia and south of Three Rivers. He then returned to Placerville.
Two years later, Tharp, along with his brother-in-law John Swanson, returned to his homestead and built a log cabin and barn, Cattle Cabin. Tharp then sought cattle summer pasturage. Led by the local Yokut Indians, Tharp "discovered" Crescent Meadow and Log Meadow near the Giant Forest. He claimed grazing rights there for several years.
Tharp's Log is a home Tharp built in a hollowed Giant sequoia (Sequoiadendron gigantuem) log at Log Meadow. It is restored and visited by tourists in Sequoia National Park today, and is on the National Register of Historic Places.