Callahan is an unincorporated community in Siskiyou County, California, United States. Callahan is located on California State Route 3 11.5 miles (18.5 km) south-southeast of Etna. Callahan has a post office with ZIP code 96014. The post office opened as Callahan's Ranch in 1858 and changed its name to Callahan in 1892. The community was named after M.B. Callahan, who opened a travelers' stop[clarification needed] in the community in 1851.