I'm not a fan of white so I most often use off white muslin or a very faint print on off white. The unbleached muslin would be true to the time period but make sure you buy as much as you will need at one time because it is a bear to match with other of the same later on. Trust me on that. And be sure to wash it first because muslin does shrink. I'm a hand quilter so I tend to use lots of muslin for backs, it's easier to quilt through. Can't wait to see the quilt.