 The lower–elevation communities of Horseshoe Bend (Payette River) and Boise (Boise River) were staging areas for the Boise Basin mines.The county's boundaries changed several times during Idaho's territorial period.Owyhee County (Idaho's oldest) and a portion of Oneida County were carved from the southern and eastern portion of the county as it existed under Washington Territory in late December 1863 and January 1864.