Complex sentence: One visible effect of the depression was the advent of Hoovervilles, which were ramshackle assemblages on vacant lots of cardboard boxes, tents, and small rickety wooden sheds built by homeless people.
Split into simpler sentences: One visible effect of the depression was the advent of Hoovervilles. "Hooverville" was the popular name for a town of cardboard boxes, tents, and small rickety wooden sheds built by homeless people.