Muslin would be the perfect backing for quilts made in that era. Can't wait to see how you finish them and what a lovely treasure they will be.

Wow! Thanks for all the replies! I will definitely use the muslin for backing. Does anyone know which of the premium muslins would be more cost-effective for me? Considering I have 7 of these to finish I need to keep cost down, but I also don't want to skimp on them, ya know? Most of the quilts are between full and queen sized. What about the color of the quilting thread?

I wish these were actually my family's quilts. But they belong to the fiancé of one of my cousins. I believe she said one of them was over 60 years old. I know 2 of them are at least 36 years old. She is also not in any hurry to get them back, which I'm glad of. She said she has waited this long and she'll wait longer for them, LOL.

I think white or ecru colored thread would be good. Don't remember any of the quilts from my family having anything but white thread and they were hand quilted.