Sheriff Lon Matthew tells Slim and Jess that he's going to Denver to try and get some information on Kem Backer and that he'll be back in two days. Laramie, Wyoming to Denver, Colorado is approximately one hundred miles. By horseback at five miles an hour for ten hours a day would be fifty miles a day which means it would take four days in travel time alone. Plus time spent while in Denver. Six days minimum would be a very conservative estimate for a trip like this and a week would be more realistic.