airfax County moved its seat of government to Alexandria in 1752, recognizing the importance of the flourishing new port. In 1754 Virginia troops led by George Washington and drilled in Alexandria lost to French and Indian forces near modern Pittsburgh on territory claimed by both Britain and France. General Edward Braddock's ill-fated army, sent out to capture the region from France, marched from Alexandria to massacre in 1755.

After finally achieving victory in 1763, the British and Americans quarreled among themselves, resulting in the war for independence, which most Alexandrians supported. During the war, Alexandria provided supplies for the Continental Army but also suffered from the interruption of overseas trade. In 1780 the citizens replaced the trustee form of government with an elected Board of Aldermen and Common Council.

After the war, Alexandria grew rapidly as a trading and crafts center serving the growing West. To support the trade, efforts to build a canal bypassing the Potomac River rapids from Alexandria began. In 1785 disagreement between Virginia and Maryland over use of the river contributed to bringing about the Constitutional Convention of 1787. In 1790 the new federal government created the District of Columbia, which included Alexandria, effective in 1801. The end of the eighteenth century was poignantly marked by the death of Alexandria's greatest citizen, George Washington.