The US Federal Census


Philadelphia County PAGenWeb
Below are a number of links to familysearch.org which will give you direct access to Federal Census schedules. It does require you to create a free account.
 
Before you get started, you may want to read "Clues in Census Records" from the National Archives, especially if you're new to using these records. Also, even if you think you know everything to know about the 1890 being destroyed by fire, you should still find "The Fate of the 1890 Population Census" a very powerful story.