(This is an entry in the Annotated Bibliography.)
Hedlund, Catherine A. A Primer of New England Crewel Embroidery. 5th ed. Old Sturbridge Village Booklet Series. Sturbridge, Massachusetts: Old Sturbridge Village, 1973.
This tidy little book is both historical and instructional, with excellent, detailed illustrations explaining exactly how to do a variety of stitches, as well as photographs of extant items. It seems like an excellent resource on the subject at hand, wool embroidery, and perhaps would be relevant for broader embroidery subjects, but I am not familiar enough with the subject to be able to make that judgement. It comes from a reputable museum, Old Sturbridge Village, though the publication is somewhat dated. It is instructional as well as historical. It contains monochrome images. It does not have a bibliography.