By definition, "heirlooms" are open pollinated. Probably the only definition of "heirlooms" that is not contested. A lot of the offerings on the market are recent developments, so read the threads on the tomato forum and look at reputable "heirloom" vendors if you want family "heirlooms".

An heirloom is always open pollinated, but not every open pollinated cultivar is an heirloom. Be careful of marketing ploys used by companies labeling anything and everything they can an "heirloom" and also watch out for some seeds that are not described as a heritage variety but actually are.

I think you will be pleased with seed that you purchase from any reputable seed company. I've planted many heirlooms over the years from various sources and haven't been disappointed.

There's a lot of really historical varieties out there still pretty widely available, if that is what your interested in. There is a company out in Arizona that specializes in American Indian heirlooms some strains of which I imagine could easily predate Columbus, I'd have to find the name of it though.

For the most extensive and exhaustive list of available true heirloom seeds of all sorts, the Seed Savers Exchange is the best. One can order from a pretty good selection in their commercial catalog even without joining, but members receive the Yearbook each spring. The 2013 edition listed 12,495 varieties offered by 693 members from all 50 U.S. states plus 12 countries. Cannot get more choice than that... :-) Lots more info at their website, linked below.

Here is a link that might be useful: Seed Savers Exchange

Seed Savers Exchange will give you lots of history about many of the seeds they sell. A must-read catalog. If you become a member you can buy seeds from other members and get even more history. I plan to do that next year.

Sandhill Preservation
Bakers Creek
Southern Exposure
Johnny's Selected Seed
Fedco
High Mowing

You can find them on this webpage.

http://www.selectedplants.com/seedsupplies.htm