The general route for Interstate Highway 90 through South Dakota was established in 1955. While on the Senate Appropriations Committee, Senator Mundt received hundreds of letters regarding transportation in South Dakota. As the construction of two Interstate Systems in the state of South Dakota was an important undertaking, many South Dakotan citizens were concerned about a variety of issues.
Letters sent to Senator Mundt specifically inquired about many topics. Over time, these letters progressed from the need of having an Interstate System in South Dakota, to the splitting of land and other farming concerns (such as cattle moving and drainage), to damages incurred on land due to the construction of the Interstates. Another big issue was of specific exchanges of both Interstate 90 and later Interstate 29. Where the exchanges were to be located affected many functions ranging from business to recreation and would greatly affect small towns.
There was much concern about the routing of Interstate 90 around Spearfish and on to the Wyoming line. One option was called "Alternative C." This route would be constructed through the Spearfish Valley. Many citizens of the area were concerned about the disruption it would cause to the lovely Spearfish Valley (now called "Spearfish Canyon"). They proposed an "Alternative P" which would use a stretch of highway already constructed and used around the Spearfish Valley.
Senator Mundt, being an avid conversationalist, responded immediately to the issue. He worked with the Bureau of Public Roads and used his position as Senator and Appropriations Committee Member to ensure that all possible routes for both I-90 and I-29 were considered.
- Letters to Senator Karl E. Mundt's. Correspondence. Mundt Archives RGI DB 231-232, Madision, SD.