Google 'American Rhododendron Society'and click on 'Plant Data'. You can search for white as the predominate color and get a list of a great many species and varieties.

It is, however, a little unclear what you're looking for. 'Purple Gem' is a low growing, small leaved (lepidote) rhododendron while Chionides and Calsap are large leafed (elepidote) types which will grow very large, especially Calsap.

Thank you. When I google white rhododendrons I get a lot of adds. I knew there was a resource like that for clematis but didn't know about this for Rhododendrons. That will help tremendously.
As far as what I was looking for, I am making a mixed shrub bed. It's rather large. The larger rhododendrons are in the back/middle of the beds. I am looking for a small Rhododdenron type for the front. Purple gem would be perfect if it was white.
Thanks for taking the time to answer. I'm off to google more :)

Wow! There are a ton of different whites out there! I never knew there was so much variety in rhododendrons. Thanks :)

What you are looking for is a low white lepidote. I think Dora Amateis is an excellent choice. Wyanokie is a little later but excellent also.

Dora Amateis: EM, 3', -15F, White
Wyanokie: M. 2', -15F, White

Purple Gem: EM, 2', -20F, Purple

Thank you Rhodyman. I have to admit I was getting overwhelmed with all the information about white Rhodies. Thanks for narrowing it down :)

April Snow and April White are small leaved with double white flowers, but they have a much more upright growth habit than Purple Gem. Good larger growing large leafed varieties for background planting would include Boule de Neige, Wynterset White, Ice Cube and perhaps Catawbiense Album which grows very large.

There are a number of yakusimanum selections which are compact and slow growing. I'd particularly recommend 'Van Zile'. Flowers open with pink highlights, but quickly change to pure white. The real bonus is the white indumentum on the new leaves which really does last for pretty much the entire summer. My oldest one is 4' in height by 7' in width after 20+ years.

Thank you for all the extra info akamainegrower! I appreciate it. It really helps to have it narrower down. There's so much info out there. Overwhelming at times. Thanks again!