Railroads helped connect the east and the west
The abolitionist movement was a movement in the United States and also in Europe that sought to abolish or end the slave trade and to free slaves. Two early abolitionists in the United States were Thomas Jefferson and Benjamin Franklin, however, their positions were rather contradictory given that each was a slaveholder. Benjamin Franklin was a leading member of the Pennsylvania Society for the Abolition of Slavery, a leading early abolitionist organization. Later in the 1800s the abolitionist movement in the North was led by social reformers such as William Lloyd Garrison founder of the American Anti-Slavery Society. Additionally writers like Harriet Beecher Stowe and John Greenleaf Whittier were also active abolitionists. There were also many black abolitionist activists such as Frederick Douglass and Charles Henry Langston. The Emancipation Proclamation issued during the Civil War freed slaves in the confederate states, however, slavery was not officially ended until the 13th Amendment was passed in December 1865 which outlawed slavery.
The two major factors that contributed to England's establishment of colonies on the north american continent was an overgrowth of population in England, and the desire to cultivate and export crops to increase revenue.
Very early societies did not have a written language or even ways to efficienly preserve information, so we can reject the options "maps" and "written records".
As far as the other two options go - ice core samples and tree rings, both are correct! probably "ice core" samples are the better answer, since only fossilized tree rings would tell us about the very early societies.
The answer is Improved transportation
