Making sure Philadelphians get where they need to go - Philadelphia boasts one of the most robust mass transportation systems in the nation. One quarter of all Philadelphians ride transit to work on one of the most diverse set of transit systems in the country. They have the choice of catching trolleys, subways, commuter rail or buses to get where they are going. These photos allow us to step back into time and look at how this transportation system grew from the early trains serving northwest Philadelphia to the first buses that crossed the entire city.