Major Walter Reed's discovery in 1900 that mosquitoes spread yellow fever halted an outbreak and led to the disease's eventual eradication.
During the Great Depression, Americans built the Hoover Dam, one of the greatest engineering works in history.
The most daring and innovative accomplishment at the turn of the 20th century.
Originally settled as a mail stop, Las Vegas changed from an Old West vacation town, to a mafia haven, to the "Atomic City" and "Sin City."
"The Wizard of Menlo Park," Inventor Thomas Edison, built the first practical light bulb and revolutionized the world.
George Eastman introduced the Kodak and Brownie camera systems and transformed photography into something anybody could do.
The internationally famous carnival of delights in New York was the birthplace of the hot dog and the roller coaster.
Brothers Wilbur and Orville Wright built a flying machine that made its first flight in Kitty Hawk, North Carolina in 1903.