Mark Zabel asked me to assist you in your effort to find the source of the Vermillion River. Im going to try to help, but this is not an easy task. The Vermillion is fed by groundwater springs and seeps in numerous locations on multiple branches and tributaries which additively collect to form the Vermillion that is known in the middle (Farmington) and lower portions (Hastings/Red Wing) of the watershed. The Vermillion Rivers main stem currently originates from a wastewater treatment plant in Elko New Market. The discharge from this plant is currently ditched and transported to the Vermillion River through ditches that likely originated from wetland draining for agricultural production starting in approximately 1960. I know that sounds a bit weird, but it does indeed feed the main stem of the Vermillion with a continuous flow of water. Previous to the time of the plant, it likely originated from wetland springs just upstream of Rice Lake in Eureka Township (0.4 miles south of Logan Way and 0.2 miles west of Interstate 35). My suggestion is to download a program called Google earth from the web so you can better find these locations. This free program will allow you to look at current air photos from these locations, road names, etc. It will also allow you to put the following coordinates in to locate the springs I mentioned above: 44.607230 , -93.298671. You can place these right into the search or fly to box and the program will find them.
Looking at historical photos that I could find, it appears the above mentioned information was the case (see the attached air photos circa 1951 and 1964). I hope this helps you in your quest. If you have any other questions, let me know and Ill see how I can help.