It has 18,661 sq mi (48,300 km2), or 16.4% of Arizona's total area, and is larger than the nine smallest states in the U.S. Coconino County comprises the Flagstaff metropolitan statistical area, Grand Canyon National Park, the federally recognized Havasupai Nation, and parts of the federally recognized Navajo, Hualapai, and Hopi nations.

The county was the setting for George Herriman's early 20th-century Krazy Kat comic strip.

After European Americans completed the Atlantic & Pacific Railroad in 1883, the region of northern Yavapai County began to undergo rapid growth.

The people of the northern reaches had tired of the rigors of traveling to Prescott to conduct county business.

This did not take place, but Coconino County was formed in 1891 and its seat was designated as Flagstaff.

It has more land area than each of the following states: Connecticut, Delaware, Hawaii, Maryland, Massachusetts, New Hampshire, New Jersey, Rhode Island, and Vermont.

In descending order of area within the county, the reservations are the Navajo, Hualapai, Hopi, Havasupai, and Kaibab.

It is the only county from any state west of the Mississippi River – apart from Black Belt Madison Parish and Tensas Parish which are directly adjacent to that river – that voted for Barry Goldwater in 1964 but has since voted for the Democratic nominee in the eight most recent presidential elections.

The cities of Williams and Page and surrounding areas, on the other hand, trend Republican.

Routes 89 and 180 extend north from Flagstaff and connect it with the Grand Canyon National Park.

Flagstaff Pulliam Airport is a public airport located four miles (6.4 km) south of the central business district of Flagstaff, it is mostly used for general aviation but is also served by two commercial airlines.

Amtrak has a passenger railroad stations in Flagstaff and formerly in Williams, with daily service on the Southwest Chief to the east towards Chicago, and to the west towards Los Angeles.

The Mountain Line provides public transportation bus service in the Flagstaff area.

Elementary: According to Coconino County's parcel viewer, some reservation areas are in the "Unorganized School District #00".