The answer is urbanization.
A military action the added territory in the United States in 1848 was the Treaty of Guadalupe Hidalgo. It ended the Mexican-American war and added the territories California, Arizona, Colorado, New Mexico, Nevada, Utah, and Wyoming.
The house of reps changing due to the change in population in each state which is measured every few years
Trade route from Europe to China had always been a land route before the discovery of sea route in 15th century.
