In 1858 Crapo moved to Flint, Michigan, primarily due to investments in pinelands, and became Flint's mayor in 1860. His family established a lucrative lumbering business in the area, which by the beginning of the Civil War was one of the largest individually owned lumber firms in the state. He served as mayor until 1861. He was instrumental in the construction of the Flint and Holly Railroad, and was President of that corporation until its consolidation with the Flint and Pere Marquette Railroad. The line is now the CSX Saginaw Subdivision and leased by Lake State Railway.