Colonial history of the United States Lower Louisiana. This vast tract was first settled at Mobile and Biloxi around 1700, and continued to grow when 7,000 French immigrants founded New Orleans in 1718. Settlement proceeded very slowly; New Orleans became an important port as the gateway to the Mississippi River, but there was little other economic development because the city lacked a prosperous hinterland. In 1763, Louisiana was ceded to Spain around New Orleans and west of the Mississippi River. In the 1780s, the western border of the newly independent United States stretched to the Mississippi River. The United States reached an agreement with Spain for
France–Spain relations Western Flanders, roughly equivalent to the modern French department of Nord, was also ceded. An anomaly of the treaty was that although all villages in Roussillon were ceded to France, Llívia was deemed to be a city and was therefore retained by Spain to the present day as an exclave into France. The treaty was signed on Pheasant Island, an uninhabited, unserviced island in the Bidasoa river between the French commune of Hendaye and the Spanish municipality of Irun. Both settlements, and therefore their countries, took sovereignty of the island for six months out of each year. After Philip IV