Geography
According to the U.S. Census Bureau, the county has a total area of 1,229 km² (474 mi²). 1,183 km² (457 mi²) of it is land and 46 km² (18 mi²) of it (3.71%) is water. Its northern boundary is defined by the Kansas River which provides hydropower at the Bowersock Dam.

Demographics
As of the census² of 2000, there were 99,962 people, 38,486 households, and 21,167 families residing in the county. The population density was 84/km² (219/mi²). There were 40,250 housing units at an average density of 34/km² (88/mi²). The racial makeup of the county was 86.09% White, 4.24% Black or African American, 2.56% Native American, 3.12% Asian, 0.06% Pacific Islander, 1.20% from other races, and 2.73% from two or more races. 3.27% of the population were Hispanic or Latino of any race.

There were 38,486 households out of which 27.40% had children under the age of 18 living with them, 43.10% were married couples living together, 8.50% had a female householder with no husband present, and 45.00% were non-families. 28.50% of all households were made up of individuals and 5.80% had someone living alone who was 65 years of age or older. The average household size was 2.37 and the average family size was 2.97.

In the county the population was spread out with 20.40% under the age of 18, 26.40% from 18 to 24, 28.30% from 25 to 44, 16.90% from 45 to 64, and 7.90% who were 65 years of age or older. The median age was 27 years. For every 100 females there were 98.70 males. For every 100 females age 18 and over, there were 97.70 males.

The median income for a household in the county was $37,547, and the median income for a family was $53,991. Males had a median income of $35,577 versus $27,225 for females. The per capita income for the county was $19,952. About 6.20% of families and 15.90% of the population were below the poverty line, including 9.00% of those under age 18 and 7.30% of those age 65 or over.

Cities and towns
Incorporated cities

Name and population (2004 estimate):

Lawrence, 81,873 (county seat)
Eudora, 5,119
Baldwin City, 3,664
Lecompton, 599

Unincorporated places
Big Springs
Clearfield
Clinton
Globe
Grover
Hesper
Kanwaka
Lake View
Lone Star
Midland
Pleasant Grove
Sibleyville
Stull
Vinland
Worden