Croco Post Office was established 05 Sept 1881 and discontinued 08 June 1883. The first postmaster was James Blue. Croco is shown on the map included in William G. Cutler's History of the State of Kansas, first published in 1883 by A. T. Andreas, Chicago, IL. It is located in Rock Branch township in the northwestern part of the county. See the map at http://history.cc.ukans.edu/carrie/kancoll/graphics/maps/norton.htm I speculate that Croco was named for William H. Croco came to Norton County in 1878 and was Sheriff from 1897 - 1899. He was under-sheriff at the time F. M. Lockard's book "The History of the Early Settlement of Norton County, Kansas" was published in 1894. If you have any further information on Croco, please share it with us all. Thanks, Ardie