June 14, 1775 is considered the birthday of the United States Army.
Reportedly, at John Adams’ request, Congress voted to “adopt” the Boston troops on June 14, although there is no written record of this decision. Also on this day, Congress resolved to form a committee “to bring in a draft of rules and regulations for the government of the Army,” and voted $2,000,000 to support the forces around Boston, and those at New York City. Moreover, Congress authorized the formation of ten companies of expert riflemen from Pennsylvania, Maryland, and Virginia, which were directed to march to Boston to support the New England militia.
George Washington received his appointment as commander-in-chief of the Continental Army the next day, and formally took command at Boston on July 3, 1775.—John R. Maass, Historian
US Army Center of Military History
June 14 is also Flag Day, marking the day in 1777 when Congress authorized the “Stars and Stripes.”