The county is 40% rural and 60% urban owing to Nairobi’s consistent growth Northwards. The Kikuyu are the dominant tribe in the county.
In 2007, Kiambu District was subdivided in two: Kiambu East and Kiambu West. Kiambu West district took Limuru, Lari and Kikuyu divisions, with Limuru as its district capital.
According to the 2019 census, there is a total population of 2,417,735 in the county: 1,187,146 males, 1,230,454 females, and 135 intersex persons. There are 796,241 households with an average household size of 3.0 persons per household and a population density of 952 people/km2.