After spending several years of practicing law in Hannibal, Hatch ran for Congress as a Democrat in 1878 and won the first of eight successive terms. During this time he served as chairman of the Committee on Agriculture. In addition to the Hatch Act, he implemented reforms in federally mandated food inspections, and established national standards in animal hygiene control. He tried and failed to become Speaker of the House in 1892 as well as Secretary of Agriculture.
Hatch returned to Hannibal in 1895 after his term ended. He ran his farm there until he passed away on December 23, 1896.