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
New Spain Spanish Conspiracy, hoped to gain greater control of Louisiana and all of the west. These hopes ended when Spain was pressured into signing Pinckney's Treaty in 1795. France re-acquired Louisiana from Spain in the secret Treaty of San Ildefonso in 1800. The United States bought the territory from France in the Louisiana Purchase of 1803. New Spain claimed the entire west coast of North America and therefore considered the Russian fur trading activity in Alaska, which began in the middle to late 18th century, an encroachment and threat. Likewise, the exploration of the northwest coast by Captain James Cook of