Johnson entered West Point in 1899, and graduated and was commissioned a second lieutenant in the 1st Cavalry on June 11, 1903. Douglas MacArthur was one of his West Point classmates. From 1907 to 1909 he was stationed at Pampanga, Philippines, but later was transferred to California. In the early years of the 20th century, most national parks in the United States were administered by units of the United States Army. Johnson was subsequently stationed at Yosemite and Sequoia national parks. He was promoted to first lieutenant on March 11, 1911, and was named superintendent of Sequoia National Park in 1912.