On a recent trip to downtown Brooklyn, I stumbled upon the New York Transit Museum (http://www.mta.info/mta/museum/). I didn't have a lot of time, but was really impressed with what I saw. I took a bunch of photos (phone quality, sorry) of some of the subway car interiors, which had the ads from that era installed. It was really fun to see so much fantastic illustration and typography. Check their website for location and times, and bring a camera better than an old iPhone. Cost $6
What follows are a bunch of phone pics from my hurried visit. I didn't even make it through the entire museum but I was able to get the general idea. They also had a gallery with a lot of original framed art from the MTA poster series. I opted out of photographing and posting those (except for one group pic near the bottom), as many of those pieces are from contemporary illustrators (some of you) and it just didn't feel right without having the time to get all the details/credits correct .... so I focused on the vintage art and misc. bits and pieces. That said, it's worth the trip just to take in the original art gallery section of the museum.
(http://www.mta.info/mta/aft/) has a link for artist opportunities with MTA poster art and more. enjoy!