>>1128783US based websites that are heirloom and preferably organic. It really doesn't matter which one. The two that has the most of what I get are:
http://sustainableseedco.com/https://www.rareseeds.com/I did use Burpee for a long time before the internet, but I had way too much trouble with their stuff. Now I don't use them at all. The local stores all have the same brands of seeds with really shitty germination rates. Only things like corn, squash, and watermelon seeds have had good germination from the local stores. I do a fair amount of seed trading with local gardeners/farmers. That's the best way since their crops are proven in your area. I'll be traveling around the county next spring taking 100s of fruit tree cuttings from family and friends' trees.
Once I have a large enough seed bank, I'll be able to simply save seeds and make cuttings from all my own plants without the need for outside sources. Though, I'm always experimenting with something new. My largest problem is having a proper place to store root crops over winter for spring planting.