Monsanto's stated agenda of totally monopolizing agricultural seeding started in the late 1980s. That's when the Bush Senior administration granted fast track product approval to the industry, which translates to minimal or no third party oversight and no long term testing.
Monsanto's earlier legacy includes a list of chemical toxins that pollute the environment and food additives that endanger human health. The planetary trail of diseased and dead bodies numbers in the millions. For a complete time line of Monsanto's atrocities see "Monsanto's Dark History: 1901 - 2011."
Even with its destructive track record, Monsanto has managed to successfully push its current agricultural agenda with intense lobbying, cleverly manipulating the revolving corporate/government doors of the FDA and USDA, and even attempting to bully key government officials of other nations.