The Stock Exchange’s present home on Wall Street did not open until 1903, but trading in stocks began well before that. By the time this building became its headquarters, the Exchange had already been in existence for more than a hundred years. Today, people trade hundreds of millions of shares electronically as well as by the floor broker system. Visitors can watch the action on the floor from a viewing gallery. Multi-media exhibits help explain the frenzy below. Admission is free.