Adjacent counties

• San Juan County - north
• Sandoval County - east
• Cibola County - south
• Apache County, Arizona - west

Major highways

• Interstate 40
• U.S. Route 491 (formerly )
• New Mexico Highway 264
• New Mexico Highway 371
• New Mexico Highway 602

National protected areas

• Chaco Culture National Historical Park (part)
• Cibola National Forest (part)

Census-designated places

For purposes of census-data collection, organization and analysis, the United States Census Bureau has devised 44 census-designated places since 1980 within McKinley County.

2000 census

As of the 2000 census,^[10] 74,798 people, 21,476 households, and 16,686 families were living in the county. The population density was 14 people per square mile (5.4 people/km²). The 26,718 housing units had an average density of 5 units per square mile (1.9 units/km²). The racial makeup of the county was 74.72% Native American, 16.39% White, 0.46% Asian, 0.40% African American, 0.04% Pacific Islander, 5.47% from other races, and 2.52% from two or more races. About 12.40% of the population were Hispanics or Latinos of any race.

Of the 21,476 households, 46.0% had children under 18 living with them, 47.7% were married couples living together, 22.7% had a female householder with no husband present, and 22.3% were not families. About 19.5% of all households were made up of individuals, and 5.3% had someone living alone who was 65 or older. The average household size was 3.44, and the average family size was 3.99.

In the county, the age distribution was 38.0% under 18, 9.7% from 18 to 24, 27.8% from 25 to 44, 17.6% from 45 to 64, and 6.9% who were 65 or older. The median age was 27 years. For every 100 females, there were 93.50 males. For every 100.0 females 18 and over, there were 89.3 males.

The median income for a household in the county was $25,005, and for a family was $26,806. Males had a median income of $26,963 versus $21,014 for females. The per capita income for the county was $9,872. About 31.9% of families and 36.1% of the population were below the poverty line, including 42.3% of those under 18 and 31.5% of those 65 or over. The county's per capita income makes it one of the poorest counties in the United States.

McKinley County is one of only 38 county-level census divisions of the United States where the most spoken language is not English and one of only three where it is neither English nor Spanish; 45.75% of the population speak Navajo at home, followed by English at 38.87%, Zuñi at 9.03%, and Spanish at 5.72%.

2010 census

As of the 2010 census, 71,492 people, 21,968 households, and 16,219 families resided in the county.^[11] The population density was 13.1 inhabitants per square mile (5.1/km²). The 25,813 housing units had an average density of 4.7/sq mi (1.8/km²).^[12] The racial makeup of the county was 75.5% Native American, 15.2% White, 0.8% Asian, 0.5% Black or African American, 4.9% from other races, and 3.1% from two or more races. Those of Hispanic or Latino origin made up 13.3% of the population.^[11]

Of the 21,968 households, 46.2% had children under 18 living with them, 40.8% were married couples living together, 24.5% had a female householder with no husband present, 26.2% were not families, and 22.4% of all households were made up of individuals. The average household size was 3.22, and the average family size was 3.82. The median age was 30.7 years.^[11]

The median income for a household in the county was $31,335 and for a family was $37,345. Males had a median income of $31,527 versus $26,236 for females. The per capita income for the county was $12,932. About 26.6% of families and 33.4% of the population were below the poverty line, including 43.0% of those under 18 and 31.3% of those 65 or over.^[13]

City

• Gallup (county seat)

Unincorporated communities