The Eastern US species are rarely offered for sale. The nursery linked below lists Erythronium americanum, but I haven't purchased those from them. That species is so shy flowering that I only have a few, for curiosity sake.
Bulb companies usually only sell western species, E. californicum, E. revolutum, E. tuolumnense and their cultivars & hybrids, such as 'Pagoda', 'White Beauty' & 'Citronella' and the Euro species; E. dens-canis and it's cultivars.
You might also try the Native Plant & Plant Exchange Forums, as I have seen some native one's offered there at times or post your wants there.
Good luck!

Here is a link that might be useful: Wildflowers

And I am looking for some books or articles that feature native bulbs. Anyone have a suggestion? I have combed through wildflower books, but often there is disagreement on which plant goes in what category, i.e., rhizomes or tubers, for example. And sometimes there is no indication of what type of underground structure there is. Of course, I have grown many of these plants, but I refuse to admit which ones I would probably put in the "wrong" category.

ncrescue, I would love to find a book or article on the topic of native bulbs, rhizomatous plants, etc. as well...if you find anything, please feel free to let me know.

The website link below for Pacific Rim nursery has a pretty good index of bulbs, etc. I was going to order Erythronium americanum from them, but then realized I missed the Aug 31 deadline, and they are also in Canada. It's a nursery, but the descriptions are pretty extensive as far as the plant structure etc. They do have a lot of Western species, but do have some Eastern species listed as well.

Pacific Rim nursery:
http://www.hillkeep.ca/bulbs%20main.htm#BULBS%20INDEX%C2%A0

I also like to use the Lady Bird Johnson Wildflower Center website:
http://www.wildflower.org/plants/search.php?start=0amp;pagecount=10&pagecount=100

Unfortunately, they don't have a "bulbs" or "rhizomatous" category, but you can search by Family in Liliaceae/Lily Family and it will bring up most of the native plants like Erythronium, Trillium, etc. The beginning paragraph usually has some info about what the underground root structure is like, although sometimes it can be somewhat vague.

Anyway, thank you ladywindsurfer for the link. I will check that nursery out.

There is a book called Bulbs of North America by Jane McGary that is quite informative. I borrowed it from our local library. see link below

Here is a link that might be useful: native bulb book

Thanks so much for the Bulbs of North America link ontnative...it looks really informative. Maybe they might have it at our library too? I will check. Thanks again.

Thanks. I just ordered the NARGS book, the one you recommended, from Amazon. I had tried Timber Press, the original publisher, but they no longer had it listed.

Unfortuately, once on-line with Amazon, I ordered a few other goodies, too. Guess they will be my winter/Christmas me-to-me present.

Try MunchkinNursery.com