The birth of modernism and modern art can be traced back to the Industrial Revolution, a period that lasted from the 18th to the 19th century, in which rapid changes in manufacturing, transportation, and technology profoundly affected the social, economic, and cultural conditions of life in Western Europe, North America, and eventually the world. New forms of transportation, including the railroad, the steam engine, and the subway changed the way people lived, worked, and traveled, both at home and abroad, expanding their worldview and access to new ideas. As urban centers prospered, workers flocked to cities for industrial jobs, and urban populations boomed. Prior to the 19th century, artists were most often commissioned to make artwork by wealthy patrons, or institutions like the church. Much of this art depicted religious or mythological scenes that told stories and were intended to instruct the viewer. During the 19th century, many artists started to make art about people, places, or ideas that interested them, and of which they had direct experience. With the publication of psychologist Sigmund Freud's The Interpretation of Dreams (1899) and the popularization of the idea of a subconscious mind, many artists began exploring dreams, symbolism, and personal iconography as avenues for the depiction of their subjective experiences.