A Field Guide to Wildflowers: Northeastern and North-Central North America (Peterson Field Guides)

Paperback by Roger Tory Peterson.  448 pp.  Covers 1,293 species in 84 families. Illustrations throughout (b/w and color).

Grouped by color and by plant characteristics, 1,293 species in 84 families are described and illustrated. Included here are all the flowers you're most likely to encounter in the eastern and north-central U.S., westward to the Dakotas and southward to North Carolina and Arkansas, as well as the adjacent parts of Canada.