I sure wish I could tell you where I got it, but a good book on engraving designs is "A Sketchbook of Colonial and Early American Powder Horn Engraving Designs:1740-1800" by Lee A. Larkin. GREAT BOOK! Also gets Madison Grant's "Powder Horns and Their Architecture", another "must have" for horn makers IMHO. Depending on the area of interest for you on maps, I did a Google and also went to the local library and found maps on my home area for the period of 1750 and another for 1810. Certain things you know you could be added to the map or subtracted as you went from 1750 to 1810. Any rate, I made a map horn (well my daughter did the engraving) of my home area, Ohio from the Ohio River to Lake Erie up the Miami River, St.Mary's and Maumee rivers. The people at the local library really knocked themselves out looking also for this map project.