<span>) The population has increased because of the immigration and slaves.
2) The population grew in leaps and bounds, primarily through immigration.
3) Roads, waterways, railroads, steam boats, and refrigerator railroad cars.
4) * Changes in transportation played a big part in the change of United States.
* The change in the industry such as more factories being opened.
* Many women had made progress in doing things that men would usually do.
* Changes were made to the Constitution.
5) The 14th Amendment had defined a citizen as "any person born or naturalized in the U.S." The 13th Amendment abolished slavery, and the15th Amendment prohibits the right to vote to someone due to their race, color,or servitude. </span>
Answer:
By 1860, 30,000 miles (49,000 km) of railroad tracks had been laid,.
By 1860, 30,000 miles (49,000 km) of railroad tracks had been laid, with 21,300 miles (34,000 km) concentrated in the northeast.
