The Master Gardener program's roots date back to the presidency of Abraham Lincoln, who signed the Morrill Land-Grant College Act, which essentially was a farm-grant program since the country was mostly agricultural in those days.
The act granted to each state 30,000 acres of public land for each of its Senators and Representatives. Not for them, personally, it's just that that's how they calculated how much to give each state. Proceeds from the sale of that land were to be invested in a perpetual endowment that would support the creation of colleges in each state that would educate people in agriculture and mechanical arts.
Those colleges were called federal land-grant colleges. In New Jersey the land-grant college is Rutgers; in Connecticut, UConn, in New York, it's Cornell. (For a complete list of the 46 land-grant colleges, click here.)
In 1972, agents in the Washington state system began training volunteers to answer questions from home gardeners, free of charge. And thus, the Master Gardener program was born.
