Henry Harmon Clark was born on February 5, 1824, in Granville, Massachusetts. He attended public schools there, helped his father on the family farm, and later worked as a carpenter. Clark and his brother, Sanford, went by the Isthmus of Panama to the California gold fields in 1850, and mined successfully for 2 1/2 years on the North Yuba River. In 1853, Henry returned to Massachusetts, married, and moved to Independence, Iowa, where he engaged in farming and stock raising. In 1864, Clark traveled overland to Virginia City, Montana Territory, with Cornelius Hedges and Timothy Wilcox. Wilcox began farming near Virginia City. Hedges and Clark worked for wages in the mines and later became partners in the operation of a placer mining claim they had purchased. The partners moved to Helena's Last Chance Gulch in 1865. After working for wages for a period of time, Clark began farming in the Prickly Pear Valley near Helena. In 1867, his wife, Emily, and their two children, James and Jennie, traveled up the Missouri River with Mrs. Cornelius Hedges, Mrs. Timothy Wilcox, and Wells T. Clark. After farming for eight years, Henry Clark bought the Prickly Pear House, located in what is now the town of East Helena, and operated it as a hotel, road house, and tavern. He continued to operate the farm on a rental basis. Clark and a Mr. Riggs platted the townsite of East Helena in 1888. Clark served as a county commissioner, a school trustee, and East Helena's first postmaster.