求翻译：殖民时期美国人口不多，独立后仅250万人。但独立后总人口增长很快，主要是欧洲移民增加的原因。到1820年，总人口已达963.8万人。从1820-1900年，移民人口已达1406.1万人。人口的迅速增加，一方面是城市人口增加，为农产品开拓了更大的市场；另一方面，也为西部开发提供了从组的劳动力。是什么意思？

The colonial period the U.S. population is small, only 2.5 million people after independence. But independent of the total population is growing rapidly, the main reason for the increase of immigrants from Europe. By 1820, the total population reached 963.8 million. From 1820-1900, the immigrant pop

colonial-era United States population is not only in the post-independence more than 2.5 million people. After independence, but population growth, mainly European migration of the reasons for the increase. In 1820, the total population has reached 9.638 million people. From 1820 - 1900, immigrant p

Colonizes the time US population not to be many, after independence only 2,500,000 people.But after the independence the total population growth is very quick, mainly is the reason which the European immigrant increases.To 1820, the total population has reached 9,638,000 people.From 1820-1900 year,

Colonial United States population is not large, only 2.5 million people after independence. But the total population growth soon after independence, mainly because of increased immigration in Europe. By 1820, the population has reached 9.638 million people. From 1820-1900, the immigrant population h