Why my recent events have led to many African-Americans working for ranchers

A During the Civil War mini African-Americans went west to work on railroads
B After the end of slavery, African-Americans could move and find new work
C In the 1850s, many free African-Americans from the north became ranchers
D During reconstruction African-American politicians promoted ranching

All of the statements A, B, C, and D provide possible explanations for why recent events have led to many African-Americans working for ranchers.