Perhaps most interesting is the range of buildings and machines that Mills designed - from monuments and local courthouses, to prisons and churches, bridges and canals, to rotary piston engines and fireproof masonry vaults - all during a revolutionary era of building technology in America.".

Some vols. include supplemental journals of "such proceedings of the sessions, as, during the time they were depending, were ordered to be kept secret, and respecting which the injunction of secrecy was afterwards taken off by the order of the House."