Weir is a city in Cherokee County, Kansas, United States. As of the 2020 census, the population of the city was 569. Weir was founded in 1872…Weir is a city in Cherokee County, Kansas, United States. As of the 2020 census, the population of the city was 569. Weir was founded in 1872. It is named after landowner T. M. Weir, who donated forty acres as a townsite. The first post office in Weir was established in 1875.