Clark County’s first inhabitants were forerunners to the Northern Shoshoni. They were mainly big game hunters and gatherers of wild food. These people used natural rock outcroppings and caves for dwellings and places for butchering and storing meat. The Nez Perce Tribe also used this general area as a route to their buffalo hunting grounds in Montana.
In the early 1800’s the area was well traveled by early trappers and explorers. In 1853 Lieutenant Mullen traveled through the Medicine Lodge Canyon from Montana into Idaho on his way to Fort Hall. This same route which was historically used by the Nez Perce became a well traveled route to and from the gold fields of Montana, into Idaho, and then further south to Salt Lake City, Utah. Birch Creek Pass and Monida Pass were well traveled. Today Monida Pass is the main route running north and south between Idaho and Montana.


Beaver Stage Station was the first settlement in Clark County. The settlement began as a stagecoach station in the early 1860’s but by 1870 was a boom town for lumber enterprises. The town thrived as a frontier community until the railroad forced the residents to move to Spencer in 1897 due to the depth of snow at Beaver Station and the need for more level ground. Beaver Canyon is located along Beaver Creek in Clark County south of the Montana border; this canyon was the route the Utah and Northern Railway used in 1880 and is still used by Union Pacific Railroad today. In the late 19th century stagecoaches would ferry tourists from the railroad station near Monida Pass to Yellowstone National Park. Union Pacific later built a branch line to Yellowstone for tourist use.


Clark County was established February 1, 1919 from a portion of Fremont County. The new county was named after Samuel K. Clark, who was an early settler on Medicine Lodge Creek and the first state senator from Clark County. The settlement of Dry Creek began in 1880 after the arrival of the first steam locomotive. Dry Creek was later named Dubois after Fred Dubois, a prominent U.S. Senator from Idaho. In 1910 Dubois boasted a population of 600 people (Historical Society, 1985). Spencer Idaho is located fourteen miles north of Dubois and was named for Hyrum H. Spencer a shipper, President of Ogden Rapid Transit, and Vice President of Amalgamated Sugar. Spencer Idaho contains the largest Opal Mine in the United States. The Spencer Opal Mine was discovered in 1948 by two deer hunters who filed a mining claim in 1952. The mine was bought by the Stetler family in 1968 and is still owned and operated by the Stetler family.


From a stagecoach station and Pony Express route, to a railroad stop, and a consistent thoroughfare for transporting goods Clark County Idaho continues to maintain its rural community setting. After losing its importance as a railroad center in 1927, with the relocation of the Roundhouse to Lima Montana, the county lost most of its population. Today the County relies on livestock and agriculture for its livelihood. The two largest communities in Clark County, Dubois and Spencer, house the majority of commercial businesses. Dubois consists of a resident population of 647 while Spencer is much smaller with a population of 38. The remainder of the county’s population lives in rural areas of the County.