提高聽力同時，你還可以了解到美國歷史上的一些重要事件。請感興趣的你一聽為快吧！

<注意>國家名大寫
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.
當它從法國購買了路易斯安那州的領(lǐng)土在1803年從西班牙購買佛羅里達州在1819年，美國的規(guī)模擴大了一倍。從1816年到1821年，創(chuàng)建了6個新的州。 1812年和1852年間，人口的三倍。隨著國家的發(fā)展，各國之間的分歧變得更加明顯。美國是一個國家文明城市和不法前沿。美國熱愛自由，但也容忍奴隸制度。差異開始產(chǎn)生問題。