Manifest Destiny is the belief of expanding westward (throughout the continent.) Settlers did this because they thought their gods would appreciate it. Some believed it was an excuse to be selfish. In 1803, Thomas Jefferson (who was the President at this time,) purchased Louisiana from the French Government for 15 million dollars. Louisiana stretched from the Mississippi River to the Rocky Mountains and from Canada to New Orleans, and it doubled the size of the United States. This was called the Louisiana Purchase. Thomas Jefferson thought expanding the nation would be a good thing. Jefferson sent two explorers, Lewis and Clark, to explore the new frontier. Many people believed it was the country’s destiny to expand. This belief was called Manifest Destiny. While the United States continued to gain more land and expand westward, there was a war with Mexico. They fought over the rights of Texas. Texas was a state of the country of Mexico since 1821, when Mexico gained their independence from Spain. However, the Texans didn’t agree with the Mexico government. In 1836, they declared independence from Mexico and reformed the Republic of Texas. Texas fought a ton of battles, including the Battle of the Alamo. After all of that, they finally gained their independence. In 1845, Texas joined the United States and claimed the 28th state. Mexico disagreed with this. President James K Polk sent troops to Texas to protect the border. A little after, Mexican and United States troops started shooting at each other. This was what caused the United States to declare war on Mexico. They declared war July 7th, 1846. Pioneers and Settlers moved out west for different reasons. Some wanted to claim land for farming, go to California to get rich (since at this time the Gold Rush was happening), or just to avoid persecution. Once they moved west, there was not so much government. In 1890, the US government said that the west had been explored. The country now had 44 states. The population of the United States grew from 5.2 million people in 1800 to 76.2 million in 1900. The telegraph was used to keep the country in touch.