Markham is a city in Cook County, Illinois, United States. The population was 12,620 at the 2000 census.
According to the United States Census Bureau, the city has a total area of 5.2 square miles (13.5 km²), all of it land.
It is claimed this area was beach 10,000 years ago. After countless ages of geologic swamps, marshes and sloughs, the prairies dominated the landscape with groves of trees, flowers, and wildlife in abundance.