Lots of possibilities. A few that come to mind (and that are relatively common): Ambassadeur, Indian Hills, Dominion.

Thank you brettttt.. Those are three that I didn't know about... The pictures of those online that I could find, all look more on the violet side. Mom's were a deep purple- either a self or bi-tone..
Autumn King, the Black Douglas and Nightfall are the closest I could find.. but again, I'm looking at pictures online..?? Hard to tell how large the flower is..

I have a NOID that might be like it, but maybe it is too "young"?

Oh, that's beautiful.. What's the one next to it? They look lovely together.
Mom's was not quite dark enough that I would consider it to be one of the "blacks"..
I was looking through old pictures last night, and realized that iris garden of my mother's was probably planted in the late 50's, not earlier, as my flawed memory originally thought. No pictures of the flowers, but the stalks were in the background of one picture to suggest that they were in the neighborhood of 40" tall, give or take....
Could yours be Superstition?

Oh, no. I also have Superstition, and it is a more modern iris than this one. Also, it is browner around the hafts than the above iris that I don't know the name of, and it is shorter. I am not sure if the first iris is 40 in tall or not, but it is one of the tallest I have. There is also a tall dark iris from 1960 called Licorice Stick that I was thinking might be the first iris, but looking at many pictures of it I thought maybe it wasn't. The falls on LS don't seem as standy-outy as the iris that I have, and they seem maybe a little broader as well. But maybe it is something for you to look at. Here is Superstition:

Hmmm. I've always used the words "purple" and "violet" interchangeably (blame Binney & Smith!), so I'm not sure what you mean when you say that the names I threw out earlier are all "more on the violet side." A few others to consider, though, all dark: Ebony Queen, Sable, and Sable Night

Ah.. Purple is equal parts of red and blue. Violet would be 3 parts red, 1 part blue... maybe not exactly... but that's the idea..
I've got Sable Night on order. Sable is actually close on color, probably not tall enough.
Lothario was another I looked at, but I don't think it's tall enough.
Been going through the Bluebird Haven catalog and finally got to "W" and found Winneshiek- It's a possibility..
I doubt that I will ever find the exact iris my mother had, but it's fun to try a lot of older varieties..
aseedapromise- I definitely need more black iris..

I was wondering the same thing about purple and violet, so now I know what you are talking about. I put up the NOID just because I thought you wanted the iris to be on the blue side of purple. I guess I took your mentioning "dark" too much to heart. I guess the definition of dark as far as iris has changed over time as hybridizers were able to get darker and darker iris. Well, at least you are learning of a lot of different black, purple and violet ones. Even if they aren't exactly like your mom's, you'll find something pleasing.

Well, color names in the nursery industry have a lot of "flexibility".
But... I went and looked at some color wheels, and was shocked to find that I've been wrong all these years. Purple is mid-way between red and blue, as I said, but violet is half-way between purple and blue, thus; bluer... not redder as I thought. Bretttt and aseedisapromise- you were right!

Go to the (google) Historic Iris Preservation Society.(hips) They have lots of pictures of historic Iris. you might be able to find something that looks like what you remember from your youth. Good Luck!!

Littlebit... I've been living on the HIPS site lately it seems... It's a great resource... Also been all over World iris and all the growers that have historics. (I really need to get a life) : )

Really? Violet is more blue? I had the same impression you did, Sherry, and have always used the word for reddish-purples. I think that's how the color has been used as a hybridizer description, because if you look, the blue-purples are not called violet, at least not that I can find. Very confusing. We need an official color chart!
Renee

Renee,
I was flabbergasted.. The word "purple" is not on the numerous color charts I pulled up. In order, red to blue: Red, red-violet, violet, violet-blue, blue.

God-bless the RHS though... They still use the word Purple:
http://www.azaleas.org/index.pl/rhsmacfan2.html

As far as I know, these are still the recognized names for colors throughout the horticultural world.

I for one, will continue to use purple instead of violet.. and violet for the color between purple and red.

I forgot to say... The RHS chart, despite using the word purple, uses violet for what I call purple...