The publication provides a method of indexing points along the main-stem South Platte River and its tributary streams. The objectives were a single procedure for the identification of point locations pertinent to data collection and a single coding system for the identification of specific parameters of water quality. The first part consists of main-stem and tributary stream mileages and includes important hydraulic features within the study area. The second part gives the river mileage locations of all established communities and cities in the State of Colorado within the confines of the South Platte River Basin.