It started with a rally at Jackson and Lasalle, outside the Federal Reserve Bank, and ended at Michigan and Congress where protestors set up tents.
Marchers were angry about Wall Street bailouts, high unemployment numbers and corporate greed among other issues. Among the protestors was an Iraq war veteran.
Occupy Wall Street protesters also flooded New York's Times Square on Saturday. More than 40 people were arrested there.
The most violent protest was in Rome, where protestors set fire to at least one building and a police van.
Other "Occupy" demonstrations were largely peaceful. Among them, more than 10,000 people gathered in Madrid.