Cyrus McCormick reportedly designed, built, and tested his reaper all within six weeks at Walnut Grove, although the design may have been merely an improvement upon the similar device developed by his father and his brother Leander over 20 years.
Cyrus McCormick is credited with designing, building, and testing his reaper in a relatively short timeframe at Walnut Grove; however, this may have been based on an improved version of a similar device created by his father and brother, Leander, years earlier.