The Army of the Potomac had its beginnings when President Lincoln called for 75,000 militia from Northern states. This was just a day after the garrison at Fort Sumter surrendered to Confederate forces. These units were to serve for 90 days and each state governor was given a quota. At the time 90 days was the maximum time militia units could serve under the Militia Act of 1795. In 1861, the regular U.S. Army only had 16,367 officers and men. They were organized into 197 companies, 179 of which were scattered in frontier duty in the west. East of the Mississippi River the remaining 18 companies were all artillery. In total there were only six generals including the General-in-Chief, Winfield Scott.