Monument is a census-designated place in northeastern Logan County, Kansas, United States. As of the 2020 census, the population was 56. It is located along U.S. Route 40, west of Oakley. Established sometime in the latter half of the 19th century, it was originally called Monument Station as it served as a stop for the overland stage and for travelers moving we…Monument is a census-designated place in northeastern Logan County, Kansas, United States. As of the 2020 census, the population was 56. It is located along U.S. Route 40, west of Oakley. Established sometime in the latter half of the 19th century, it was originally called Monument Station as it served as a stop for the overland stage and for travelers moving westward through Fort Wallace.