We never planned on ever traveling outside the United States and never had need for a passport. Shame on us for being naive about the whole process. When we first thought about the trip, we did not realize it was such a pain to get one.
Except for a couple of trips to Europe in the 1980's, I've never have been out of the US and needed a Passport. Yet I got one and renewed it ever since. (I grew up in upstate NYS and went to Canada quite often, but that was when the crossing was easy.)
When my sister and BIL flew to Asia in 2005, they needed their Passport numbers to reserve the flights.
Even though I don't plan to travel internationally, I still would rather have a Passport and/or a Passport Card and not need it than not have them and need them. (I have both.) You never know if say you find yourself in Niagara Falls, NY and want to go to Niagara Falls, ON or find yourself in Detroit and want to go to Windsor or find yourself in Seattle NTD want to spend the day in Vancouver, BC.
To the OP, if it's convenient to you and you travel is soon (I think within like 14 or 30 days), you can make an appointment to visit the Passport Office in Chicago (or wherever) and get your Passport the same day!
HINT: A Passport Card is less to obtain, if you only plan to visit Canada, Bermuda, the Carrabean and I think Mexico. But it is only good for land or sea crossings. If you fly, you'll need a regular Passport.