Rug warp is my backing of choice. It was sold to me as 60" but in reality you can count on 58″ 100% cotton. Threads per inch 11 x 13. I routinely hook wide cuts in this backing. If you have animals this is the backing to use. The loops are much more secure. Even my footstools are safe* from my cats. Order the number of yards you want. It will come in one piece that many yards long and 58″-60″ wide.
*Update: My son adopted a new dog when he was here for an extended visit. I think it stressed out my older cat. She began scratching so hard that a few tails have been pulled out. Minor damage, but not as “safe” as it was before. Now that the dog has gone home, she has stopped scratching so hard. After closer inspection, the wool is frayed, but the loops are still in place.
Wide rug warp is not just for large rugs.
58″ wide is suitable for rugs up to 46″ (6″ allowance on each side). If you hook smaller rugs, I recommend the 75″ wide because you can cut that in half to make two footstools or 2 25″ rugs.
If you buy the 58″ and hook a 25″ rug (25+6+6=37″) and cut off the excess, you only have a scrap 21″ wide. After allowing for 6″ on the edge, you can only hook something 9″ wide.
Here’s an old article about rug hooking