1700’s - Wooden plows, hoes, sickles, oxen and horse powered
                 
                1790’s - Cast iron plow, cotton gin invented
                 
                1810’s - Iron plow invented
                 
                1830’s - Reaper invented, steel plows, 300 hours of human labor to produce 100 bushels 
                 
                1840’s - factory made machinery, mowing machine invented
                 
                1850’s - 90 hours of human labor to produce 100 bushels
                 
                1860’s - First American Agricultural Revolution, steam tractors invented
                 
                1890’s - 50 hours of labor to produce 100 bushels, commercial fertilizer became popular - 1,845,900 tons used annually
                 
                1900’s - Ave. annual use of fertilizer = 3,738,300 tons, George Washington Carver advanced agriculture
                 
                1910’s - Gas tractor invented, ave. annual use of fertilizer = 6,116,700 tons
                 
                1930’s - All purpose tractor with rubber tires popular, 30 labor hours to produce 100 bushels, 1 farmer fed 9.8 people in U.S.
                 
                1940’s - Ave. annual use of fertilizer = 13,590,466 tons, 1 farmer fed 10.7 people, frozen foods became popular, Second American Agricultural Revolution (horses to machines)
                 
                1950’s - Tractors outnumbers horse for 1st time, 12 labour hours to produce 100 bushels, ave. annual use of fertilizer = 22, 340,666 tons
                 
                1960’s - 5 labor hours to produce 100 bushels, 90% of crops like beets and cotton harvested mechanically, ave. annual use of fertilizer = 32,373,713 tons, 1 farmer fed 25.6 people
                 
                1970’s -  3 labor hours to produce 100 bushels, 1 farmer fed 75.8 people
                 
                1980’s - Tractors become hi-tech,  more farmers using hi-tech methods
                 
                2000’s - 1.5 hours to produce 100 bushels, use of computers, satellites, GPS, hi-tech robots                                                                             [9]