Who headed up the American army in World War 1?

Prior to the institution of the Chief of Staff of the United States Army in 1903, there was generally a single senior-most officer in the army. From 1783, he was known simply as the Senior Officer of the United States Army, but in 1821, the title was changed to Commanding General of the United States Army. The position was abolished with the creation of the Chief of Staff of the United States Army in 1903.

The United States entered WWI after President Woodrow Wilson called for war on Germany, which the U.S. Congress declared on 6 April 1917. The Chief of Staff of the United States Army during this time was Major General Hugh M. Scott (November 17, 1914 - September 22, 1917). World War I officially ended with the The Treaty of Versailles in 1919, during which time after the tenure of MG Scott, two additional persons held the title of Chief of Staff of the United States Army--Gen. Tasker H. Bliss served from September 23, 1917 to May 19, 1918 and Gen. Peyton C. March served from May 20, 1918 to June 30, 1921.