Theodore Roosevelt became the youngest U.S. President in 1901 at age 42 after the assassination of William McKinley. As President, Roosevelt pursued progressive reforms and established himself as a trustbuster by taking on large corporations like Northern Securities Company in antitrust lawsuits. He was a conservationist who set aside 150 million acres of federal land for forests and the first national monument. Roosevelt also helped negotiate an end to the 1902 coal strike. In foreign policy, he won the Nobel Peace Prize for mediating the Russo-Japanese War and began construction of the Panama Canal. Roosevelt chose not to run for a third term in 1908.