Ellis Kepler Porter (1860 - 1936) was a photographer in Sterling, KS from about 1889 through 1930 based on the few documents that were found. There was no city directory for that town in those days, so more detailed information of his location is unavailable.
His brother Willard Duncan Porter (1854 - 1924) also worked as a photographer. According to a 1904 Kansas Gazetteer, Ellis and Willard were working together in Sterling, KS. No other documents are available to show how long this lasted.
It would be a good guess that the photographs here were done early in his career as photographer, when cabinet cards were still popular.