After graduating from the University of Michigan and Georgetown University Law School, followed by a degree in international relations from Harvard University, Quinn became a successful New York lawyer, getting involved in New York’s Tammany Hall politics, but when his candidate did not get the nomination at the 1912 Democratic National Convention he became disgusted with the whole system and became an art patron, art collector, and collector of manuscripts. His French adviser for Post-Impressionist art was Henri-Pierre Roche, who later wrote the novel "Jules et Jim". Quinn and Roche worked together to develop the famous 1913 Armory Show.