Rush County, at the south end of Post Rock Country, was organized on December 5, 1874, and named in honor of Capt. Alexander Rush, Company H, of the 2nd Kansas Colored Infantry. The first settlers arrived in 1869 and established homesteads along Walnut Creek near the Fort Hays-Fort Dodge Trail. With few trees on the vast, dry prairie, settlers searched for alternative building materials. Post Rock, a unique limestone bed that sat within inches of the surface, was so well used and became such a curiosity that it gave rise to the Post Rock Museum in 1963.