I can remember as a girl shopping with Mom there was a mixture of 36" width fabric and 42-44" fabric. I remember the patterns even having the 36" width listed, but I don't remember anything less than that.
Today while continuing to sort my mother's stash I ran across a pretty red calico and was surprised to find it was 32" width - definitely a selvage on both ends.
So what is the narrowest width you can remember?