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.
<u>Answer:</u>
Mechanized agriculture is the form of agriculture which makes use of machines to produce the output which has resulted in the increase of the productivity of the farm.
But it has certain disadvantages also like it replaces work of labor and degrades the environment by causing pollution of the land, and also leads to soil erosion which causes reduction in nutrients of soil and uprooting of trees is also done to bring more land under the farming to increase the output.
From the given options these three <span>significant black abolitionists prior to and during the Civil War
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Frederick Douglass
Harriet Tubman
Josiah Henson
Although Mary Walker is also one who should be included in the list but as the question asked, the three are above mentioned.