Allowed people to travel all across the united states. from east to west and north to south, people were traveling all over the us. in ,000 miles were built total!

If the subject this is on is refers to pre(before)-Vehicle(like cars and trucks) era, then the answer is railroads.

Railroads, walking, and horses

Britain and its empire stood alone against hitler and mussolini. in june 1941, hitler broke the non-aggression agreement with stalin and germany invaded the soviet union. in december, japan attacked the us and britain. the main lines of world war ii had formed.