Sea travel vs land travel
In pre-modern and early modern times, sea travel was so much easier and cheaper than overland travel that in the mid 19th century, traveling from the east coast of the United States to the west coast was typically done by sailing to Panama, taking a train across the short isthmus, and then sailing up to the west coast. Tens of thousands of gold rushers did this in the 1850's and 1860's (the first railroad across Panama was completed in 1855) .
- Wulf, Andrea. The Invention of Nature: Alexander von Humboldt’s New World. First American Edition. New York: Vintage Books, 2015.