The Gulf of Mexico is the ninth largest body of water in the world. Considered a smaller part of the Atlantic Ocean, it is an ocean basin largely surrounded by the North American continent and the island of Cuba. It is bounded on the northeast, north and northwest by the Gulf Coast of the United States, on the southwest and south by Mexico, and on the southeast by Cuba. The shape of its basin is roughly oval and approximately 810 nautical miles (1,500 km) wide and filled with sedimentary rocks and debris. It is part of the Atlantic Ocean through the Florida Straits between the U.S. and Cuba, and with the Caribbean Sea via the Yucatan Channel between Mexico and Cuba. Tidal ranges are extremely small due to the narrow connection with the ocean. The gulf basin is approximately 615,000 mi² (1.6 million km²). Almost half of the basin is shallow intertidal waters. At its deepest it is 14,383 ft (4,384 m) at the Sigsbee Deep, an irregular trough more than 300 nautical miles (550 km) long. It was probably formed approximately 300 million years ago as a result of the seafloor sinking. 
The first Europeans to settle the Gulf Coast were primarily the French and the Spanish. The Louisiana Purchase and the Texas Revolution made the Gulf Coast a part of the United States during first half of the 19th century. As the U.S. population continued to expand its frontiers westward, the Gulf Coast was a natural magnet in the South providing access to shipping lanes and both national and international commerce. The development of sugar and cotton production (enabled by slavery) allowed the South to prosper. By the mid 19th century, the South, including the Gulf, by some standards was populated by the nation's wealthiest people. The city of New Orleans in particular, being situated as a key to commerce on the Mississippi River and in the Gulf, had become the largest U.S. city not on the Atlantic seaboard and the fourth largest in the U.S. overall.