Walnut Grove is the landmark for the mechanical reaper. The top of the Blacksmith Shop has been converted into a museum which houses a model of a mechanical reaper. Cyrus Hall McCormick invented the first successful reaper and founded the harvesting machine industry. In July 1831, at 22 years of age, McCormick first demonstrated his invention publicly. This, the world's first successful mechanical reaper, opened a new era in agriculture, an age of mechanization that changed life on the farm.