提高听力同时，你还可以了解到美国历史上的一些重要事件。请感兴趣的你一听为快吧！

<注意>国家名大写
hints：Louisiana Territory;Florida
The U.S. doubled in size when it bought the Louisiana Territory from France in 1803 and Florida from Spain in 1819. From 1816 to 1821, six new states were created. Between 1812 and 1852, the population tripled. As the country grew, differences among the states became more obvious. The United States was a country of civilized cities and lawless frontiers. The United States loved freedom but also tolerated slavery. The differences began to create problems.
当它从法国购买了路易斯安那州的领土在1803年从西班牙购买佛罗里达州在1819年，美国的规模扩大了一倍。从1816年到1821年，创建了6个新的州。 1812年和1852年间，人口的三倍。随着国家的发展，各国之间的分歧变得更加明显。美国是一个国家文明城市和不法前沿。美国热爱自由，但也容忍奴隶制度。差异开始产生问题。