Question: What is the population of the county that contains the unincorporated community of Riverside? 
Context: Arlington Station (formerly, Arlington) is a former unincorporated community, now annexed to Riverside in Riverside County, California.  It lies at an elevation of 817 feet (249 m).  Arlington Station is located on the Atchison, Topeka and Santa Fe Railroad, 6 mi southwest of downtown Riverside. Gratiot ( ) is a town in Lafayette County, Wisconsin, United States.  The population was 653 at the 2000 census.  The Village of Gratiot is located within the town.  The unincorporated community of Riverside is also located in the town.  The unincorporated community of Dunbarton is also partially in the town. Riverside is an unincorporated community in Ravalli County, Montana, United States.  Its elevation is 3,517 feet (1,072 m), and it is located at (46.2746439, -114.1581505). Rubidoux ( ) was a census-designated place and an unincorporated community in Riverside County, California.  As of the 2010 census, the population was 34,280, up from 29,180 at the 2000 census.  Like much of the fast-growing Inland Empire Metropolitan Area, Rubidoux is rapidly changing from a rural area of quarries and dairy farms to an exurb of Riverside.  As of the 2000 Census, Rubidoux was the largest unincorporated community in the Inland Empire and in Riverside County.  On July 1, 2011, the CDP became part of the newly incorporated City of Jurupa Valley. Ravalli County is a county in the southwestern part of the U.S. state of Montana.  As of the 2010 census, the population was 40,212.  Its county seat is Hamilton. Casa Blanca, formerly known as Blanca, is a former unincorporated community now an annexed neighborhood of Riverside, in Riverside County, California.  It lies at an elevation of 866 feet (264 m).  Casa Blanca is located 4 mi south-southwest of downtown Riverside. Cleveland is a township and an unincorporated community in suburban northwestern Johnston County, North Carolina.  It lies at an elevation of 243 ft .  The settlement is also known as Cleveland Crossings, Cleveland Community, Cleveland School or 40/42, so named for the intersection of I-40 and NC 42 at the northeastern edge of the community, which serves as the primary commercial hub of the area.  NC 50 skirts the western edge of the community.  The community's population is concentrated along Cleveland Road (also known as Cleveland School Road) in Johnston County.  While officially unincorporated, postal addresses for the community generally lie in Garner (for the northern parts of the community), Clayton (in the eastern and central part of the community) and Benson (for the southern part of the community).  The community is named for the Cleveland School, a former K-12 school lying on Cleveland Road; the grounds of which currently house a community center, senior adult housing, a gymnasium and numerous athletic fields managed by the Greater Cleveland Athletic Association (GCAA), and a branch of the Johnston Community College.  Nearby unincorporated communities include McGee's Crossroads to the south along NC 50 and Willow Spring to the west along NC 42. Belvedere Heights is a former unincorporated community now annexed to Riverside, California, in Riverside County, California.  It lies at an elevation of 1237 feet (377 m).  Belvedere Heights is located 3.5 mi east of downtown Riverside. River Bend Lodge is an unincorporated community in Riverside County, California, also known as Aha Quin.  The community is near Hall Island along the Colorado River and hosts Riverside County Fire Department, Station 46.  River Bend Lodge is also inside the Mojave Desert Air Quality Management District. The South Fork Malheur River is tributary of the Malheur River in a sparsely populated part of the U.S. state of Oregon.  Arising southeast of the unincorporated community of New Princeton and slightly north of Oregon Route 78, it flows generally northeast to meet the Malheur near the unincorporated community of Riverside in Malheur County.  The South Fork enters the larger river 96 mi by water from its confluence with the Snake River.
Answer: 40,212