"American Indians selling their land" did not encourage western settlement.
Answer: Option A
Explanation:
The western settlement reached on peak between the period of 1863 and the year 1869 when transcontinental railroad got constructed and connected at Council Bluffs - the existed eastern U.S. rail networks, on San Francisco Bay, at the Oakland Long Wharf - seemed that Iowa along with Pacific coasts possess 1,912-mile continuum railroad line.
Between 1860-1870's cattle industry growth has driven the western settlement due to railroad lines availability to beef trade in the Middle West and at the East Coastal from west ranches to the population centres. The Homestead Act, signed by Abraham Lincoln, the president on 20 May 1862, facilitated Western migration by giving public lands of 160 acres for settlers.
