During which decade did transcontinental rail service begin in the united states?
a.1850–1860
b.1860–1870
c.1870–1880
d.1880–1890

1860 - 1870 ( B )

Explanation:

The FIRST Transcontinental rail service was constructed  from 1863 to 1869. it makes up part of the history of the united states of America as the first railway to connect the Pacific and Atlantic coastal areas of the western part of the united states of America. this transcontinental rail service/road was 1912 miles in length.

The transcontinental rail road was a continuous rail road that cut across cities with its terminal placed at different positions along the route which the rail service covered extensively. this transcontinental rail service aided the movement of goods and service between the areas connected by the continuous railroad. it is very big symbol in the American history in general.

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the  wilmot proviso  was designed to eliminate  slavery  within the  landacquired as a result of the mexican war (1846-48). fearing the addition of a pro-slave territory, pennsylvania congressman david  wilmot proposedhis amendment to the bill.