Patent Full Text and Image Database. (U.S. PATENT & TRADEMARK OFFICE)
Patent full-page images back to 1790. Searchable in five-year blocks back to 1976, and in one additional block covering the years 1790-1975. The 1790-1975 block contains only patent numbers and current US Classifications (in addition to links to full-page images). Patents prior to 1976 can be searched for only by patent number or current US classification.