When the United States Congress passed the Residence Act of 1790, it established a ten-mile square federal district along the Potomac River to serve as the permanent seat of the national government. To form this new capital, both Maryland and Virginia ceded land to the federal government. However, the legislation included a peculiar restriction: federal building construction was strictly prohibited on the southern side of the Potomac River, which contained Alexandria.
Over the next half-century, this geographical and statutory divide created growing economic and legal grievances for residents living in the Virginia portion of the District of Columbia. Citizens of Alexandria found themselves trapped in a constitutional gray area. They were subject to federal control yet stripped of voting representation in Congress, while simultaneously excluded from federal investments that enriched the northern, Maryland-ceded side of the capital.
Compounding these frustrations was the looming fear that Congress might ban the domestic slave trade, which formed a major pillar of Alexandria's regional economy at the time. By the 1840s, local leaders argued that the original land cession was unconstitutional because the federal government had failed to establish proper municipal operations on their side of the river. Seizing on this statutory ambiguity and mounting political pressure, Virginia petitioners rallied Congress to return the land.
In 1846, Congress passed a bill allowing the residents of Alexandria County to vote on whether to rejoin Virginia. The referendum passed overwhelmingly, resulting in the retrocession of roughly 31 square miles to Virginia. The event reshaped the geographic boundary of Washington, D.
C. into the modern, truncated diamond shape seen today, leaving behind a fascinating precedent regarding federal territorial sovereignty.