Why were the four presidents on MtRushmore chosen to be on MtRushmore?

Answer 1

The sculptor who created Mt. Rushmore, Gutzom Borglum, chose the following presidents for the following reasons:

George Washington: helped develop our national government, commanded the first army, first president

Thomas Jefferson: drafted Declaration of Independence, had vision and statesmanship, third president

Abraham Lincoln: preserved US integrity during the Civil War, sixteenth president

Theordore Roosevelt: developed the National Park System, led America into the world arena as a global political force, admired his enthusiasm, twenty-sixth president

Answer 2

The sculptor reportedly chose those particular four presidents for their "role in preserving and expanding the nation".

Washington was the commanding general of the Revolutionary forces and the first President, so leaving him off would have been almost unthinkable; Jefferson expanded the nation through the Louisiana Purchase (which included Mt. Rushmore itself), so another easy choice; Lincoln was president during the Civil War and therefore again obvious ... and then there's Roosevelt, definitely the odd man out, since during his term as President the US did not significantly expand, nor did it face any especially alarming threats.

One possible explanation is simply that he was popular. Also, Calvin Coolidge, the President at the time the construction was approved, apparently requested that, besides Washington, "two Republicans and one Democrat" be featured. (Coolidge was, himself, a Republican.)