WHO IS THE MOST IMPORTANT MAN IN AMERICA, & THEREFORE THE WORLD, IN MODERN TIMES 1900'S ON.?

"& therefore the world?" i'd say the most important men of the century were Gavrilo Princip (Bosnian) and Vladimir Lenin (Russian). keep in mind that we were not a dominant power until after WWII, and we had serious competition until the collapse of the Soviet Union.

anyway, i'd say the most important man in America was probably J. Robert Oppenheimer. Oppenheimer's invention would end WWII and define warfare for over half the century, and beyond. people like FDR did great and significant things for America, but not so much for the rest of the world. we only have a few hundred million people, so i don't think reversing a depression or something in our country is terribly significant on a global scale.

Albert Einstein

"He was the pre-eminent scientist in a century dominated by science. The touchstones of the era — the Bomb, the Big Bang, quantum physics and electronics — all bear his imprint."

http://www.time.com/time/time100/poc/magazine/albe...

Too many to pick just one, so I'll give you a few:

Martin Luther King Jr.

FDR

J.P Morgan

Bill Gates

Jackie Robinson

Thurgood Marshall

Barack Obama

Elvis Presley post-1957

Before that, Caruso, George M. Cohan, Al Jolson and Frank Sinatra