His father was the founder of Standard Oil, a shrewd businessman and the richest American of all time. Junior, as John D. Rockefeller, Jr. was called, spent his life giving money away.

One of the many endeavors funded by the younger Rockefeller was the nascent National Park System. Rockefeller was one of the single most important figures in the early days of the parks, contributing land or money to help found or expand the Great Smokey Mountains, Acadia, Shenandoah and Grand Teton national parks, according to the National Park Service. He also financed museums at Mesa Verde, Grand Canyon and Yellowstone.

Rockefeller Jr. was said to be a lover of nature, and giving money to causes they personally identify with is a common characteristic of wealthy donors, said Paul Schervish, director of the Center for Wealth and Philanthropy at Boston College.

Giving money away also helps offset substantial tax bills. Yet avoiding taxes is seldom the main reason the rich give, said Stacy Palmer, editor of The Chronicle of Philanthropy.

"It's the passion for the cause, or a religious obligation," said Palmer. When we poll people, "taxes are always [reason] ten or eleven."