President Theodore Roosevelt made this statement in Osawatomie, Kansas, on August 31, 1910. He was there to give a speech to dedicate the opening of a landmark dedicated to the abolitionist leader John Brown. The landmark was called the John Brown Memorial Park.
Interestingly, while Roosevelt was a devoted and important conservationist, his conservation remarks in this speech were tangential to the most significant thrust of it. Roosevelt, no longer president in 1910, was still wildly popular. He therefore was in Kansas to try to shore up the fortunes of the less popular President Taft and the Republican Party as a whole. His speech became controversial, as he announced his vision of what he called a "new nationalism" that would put the needs of the people ahead of the needs of property and called for a national social welfare state, which was a radical concept at the time. Conserving land was a part of that vision, but the primary thrust was much broader and would not come into actuality until his cousin Franklin Delano Roosevelt later became president and enacted the New Deal:
The American people are right in demanding that new Nationalism without which we cannot hope to deal with new problems. The new Nationalism puts the National need before sectional or personal advantage. It is impatient of the utter confusion that results from local legislatures attempting to treat National issues as local issues. …
I believe in shaping the ends of government to protect property as well as human welfare. Normally…the ends are the same, but whenever the alternative must be faced I am for men and not for property… .
In terms of actions directly relating to the conservationist impulse embodied in the quote, Roosevelt worked tirelessly for the preservation of important U.S. wilderness areas. More to the point, in 1910 he was already campaigning for the creation of the National Parks Service, which sprang into life six years later on August 25, 1916.