The Edwin Thacher papers (MC 13) document the years 1873 through 1921, representing Thacher's career as a civil engineer in bridge construction, as well as the creation of Thacher's cylindrical slide rule. Legal materials include patent specifications for the bridge truss, and a patent on concrete arches with documentation emphasizing its history and review, 1881-1899. Additional legal materials include court documentation of Edwin Thacher vs. Mayor & City Council of Baltimore regarding a patent infringement of Thacher's reinforced concrete arches, 1915, a list of infringement notices and contracts to build two bridges in Porto Rico for the United States Army, 1899. Coinciding with Thacher's patents, research and dedication to bridge work, several essays are included in the papers including publications on bridge trusses, railway bridges, columns, and concrete and steel construction. Documentation on Thacher's specifications for the engineers slide rule and a paper read before the engineers' Society of Western Pennsylvania in 1882 on the slide rule are included here. Two of Thacher's cylindrical slide rules are also part of the collection. Lastly, several postcards are also included in the Thacher papers, most of which represent the bridges Thacher was responsible for constructing with his pioneering bridge building methods.