What was the main purpose of the granger laws?

These are a string of laws that were passed by numerous Midwestern states such as Minnesota, Iowa, Wisconsin, and Illinois during the late 1860s to the early 1870s.  This was endorsed by a group of farmers known as the National Grange of the Order of Patrons of Husbandry whose objective was the regulation of the increasing prices of railroad and grain elevator companies in the aftermath of the Civil War. The outcome of the Granger Laws was different from state to state but had the same goal of making the price of railroad rates to favor small country farmers.