What was the large movement of pioneers going west across the Oregon Trail called?
A
the Oxen Train
B
the Great Escape
C
the Westward Tide
D
the Great Emigration

It effectively opened the floodgates of pioneer migration along the Oregon Trail and became known as the Great Emigration of 1843.

The Great Emigration

Explanation:

It tells on the first paragraph of the story: "Westward migration really got going with the Great Emigration of 1843".

american troops were forced to withdraw following deadly bombings.

explanation:

in the 1800s, locomotives powered by steam made transportation faster and cheaper. the resulting rapid growth of railroads led to the connection of the atlantic and pacific railroad in oklahoma city in 1897.

in the last years of the century, the improvement of steam-based engines the expansion and growth of railroads. this growth increased when the companies started to build and expand, such as the atlantic and pacific railroad, which connected new mexico with california, and missouri with oklahoma. many of these new networks were built in oklahoma, and these changes transportation henceforward.