Citizenship is an easy concept for us to understand in the modern age. When a nation emerges into being, citizenship is an underdeveloped concept. This was the case with America. This thesis investigates the early development of American citizenship from the Constitution to the passing of the Reconstruction Amendments. This thesis explores how throughout this period, American citizenship was not actively defined but instead pieced together through a series of arguments, court rulings and wars. From the Revolution emerged a new nation and with it, new citizens. The American government was at first concerned with naturalisation but as European events began to cross the Atlantic, America’s preoccupation with naturalisation gave way to an ongoing saga between America and Britain over the nature and longevity of allegiance. This difference had its roots in the Revolution but would come to the fore of American diplomacy in the early 19th century and greatly impacted the American conceptualisation of citizenship. The issue of allegiance was not solved by the two nations, but by end of the War of 1812 the matter no longer caused any tension. American citizenship, having been defined in part by external forces, was now shaped internally by the issue of admitting blacks to American citizenship. The process was arduous, involving discussions regarding rights, states’ rights, comity, race and the Constitution. These issues collapsed into one question: were blacks fit for citizenship? America’s black population resoundingly answered this by displaying the ultimate of sacrifices – dying for their country during the Civil War.