Much of the credit for the digital revolution is owed to the early pioneers of Silicon Valley -- from transistor inventor William Shockley and the Traitorous Eight to investor Sherman Fairchild, Intel CEO Andy Grove and microprocessor inventor Ted Hoff. This photo gallery features 12 men whose work and innovations helped to launch the some of the most significant technological advances in history.
The U.S. and the Soviet Union race to build the hydrogen bomb during the Cold War, thus beginning the nuclear arms race.
America came apart in 1964 and has since been reborn.
Brothers Wilbur and Orville Wright built a flying machine that made its first flight in Kitty Hawk, North Carolina in 1903.
P.T. Barnum -- huckster, con man, promoter, entertainer and founder of "The Greatest Show on Earth".
The worst epidemic in American history killed over 600,000 Americans during World War I.
The Pennsylvania Railroad Company accomplished an enormous engineering feat, but destroyed a great architectural monument.
For 21 years, Chicago mayor Richard J. Daley ruled the city, building the Sears Tower and O'Hare Airport.
The American effort to relieve starvation in Soviet Russia in 1921 during the worst natural disaster in Europe in 500 years.