McHenry County is located in the state of Illinois. As of 2000, the population was 260,077. Its county seat is Woodstock, Illinois6. Considered part of Chicagoland, McHenry County is the fastest growing county in Illinois according to the last census.
The Republican Party has maintained McHenry County as one of its most reliable strongholds, being the most conservative county in Chicagoland. No Democrat has won countywide office since before the Civil War.
McHenry County originally stretched all the way east to Lake Michigan, with the county seat centrally located in McHenry, but in 1839, the eastern townships of the county were carved out to form Lake County.
According to the U.S. Census Bureau, the county has a total area of 1,583 km² (611 mi²). 1,563 km² (604 mi²) of it is land and 20 km² (8 mi²) of it is water. The total area is 1.25% water.
As of the census2 of 2000, there are 260,077 people, 89,403 households, and 69,287 families residing in the county. The population density is 166/km² (431/mi²). There are 92,908 housing units at an average density of 59/km² (154/mi²). The racial makeup of the county is 93.91% White, 0.59% Black or African American, 0.17% Native American, 1.45% Asian, 0.02% Pacific Islander, 2.77% from other races, and 1.08% from two or more races. 7.54% of the population are Hispanic or Latino of any race.
There are 89,403 households out of which 42.90% have children under the age of 18 living with them, 66.50% are married couples living together, 7.60% have a female householder with no husband present, and 22.50% are non-families. 18.00% of all households are made up of individuals and 6.10% have someone living alone who is 65 years of age or older. The average household size is 2.89 and the average family size is 3.31.
In the county the population is spread out with 30.20% under the age of 18, 7.10% from 18 to 24, 33.50% from 25 to 44, 21.30% from 45 to 64, and 8.00% who are 65 years of age or older. The median age is 34 years. For every 100 females there are 100.70 males. For every 100 females age 18 and over, there are 98.00 males.
The median income for a household in the county is $64,826, and the median income for a family is $71,553. Males have a median income of $50,479 versus $31,141 for females. The per capita income for the county is $26,476. 3.70% of the population and 2.50% of families are below the poverty line. Out of the total population, 3.80% of those under the age of 18 and 3.60% of those 65 and older are living below the poverty line.