In the 1820’s Mexico, which had recently declared its independence from Spain, started allowing American and Northern European settlements in the territory of Texas.  By the 1830’s Northern Europeans outnumbered the Spanish and Mexican people in the region.   As a result, Santa Anna, the ruler of Mexico, forbade additional immigration and attempted to centralize the government in Mexico City.  Texans revolted, declared their independence and created the Republic of Texas. In the first election of the new country, people entitled to vote overwhelmingly favored joining the United States.  The US delayed the annexation of Texas until 1845 because of the continuing conflict surrounding slavery.

In 1840 Great Britain recognized Texas as a separate country from Mexico. This was confirmed on this map produced in London in the same year (the red dot). The Gulf of Mexico is the alternate name for what on this map is called “The Mexican Sea” (blue dot). New Orleans is shown substantially farther up the Mississippi River than it is in reality (green dot) Texas was an independent country from about 1835 to 1845 although Mexico didn’t acknowledge it and its borders were in dispute. In the south, Texas claimed its border was defined by the Rio Grande. When Texas became part of the United States, Mexico recognized its border as the Nueces River not the Rio Grande. This dispute contributed to the US-Mexican war of 1848.