Asher Benjamin's pattern books have been an important part of my research library for as long as I can remember. My copies of his 1827 and 1830 editions, reprinted by Dover Publications, are dog eared from years of use. I remember when his first book, The Country Builder's Assistant - originally published in 1797, in a small size that would have fit easily into a carpenter's pocket - was finally reprinted in 1989, and my family members gleefully gave each other copies for Christmas.
Initially, I used his books to study the trends - what builders and owners were thinking in the early 1800s - that I saw on the sea coast north of Boston, where I lived and worked. But I knew of only 2 actual copies of his designs, one in New Hampshire and another in Maine.
Then in the 1990s I happened to tour the Oliver Phelps House in Suffield, Connecticut, a house in which Asher Benjamin actually worked. Soon after that I moved to western Vermont; here I see direct copies of plates from The American Builder's Companion (first edition published in 1806), and The Architect, or Practical House Carpentry (1830). I've since acquired two later volumes as well - Practice of Architecture (1833) and The Builder's Guide (1839).
Want to read more? The wikipedia entry on Asher Benjamin has recently been updated and is a wonderful resource.