The Dred Scott Supreme Court case ruled that slaves are property and are allowed in all states/territories, even if slavery is outlawed in the state constitution.
This idea supports the concept of nullification, as states that abolished slavery would nullify (refuse) to follow this ruling because they felt it was unconstitutional.
This idea also limited the power of the federal government to restrict the expansion of slavery because the court ruled that slaves do not have legal rights and are considered property no matter where they go. This meant that slavery can essentially exist anywhere in the US and the federal government couldn't change that unless they made a national law/amendment that outlawed slavery.
City planners adopted railroad technology in the Industrial Age to help out commuters. Since a lot of factories were not located close to homes, people took the train to get to work as their way of transportation.
