NPS Form 10-900-b OMB No. 1024-0018 (Revised March 1992) United States Department of the Interior National Park Service National Register of Historic Places Multiple Property Documentation Form This form is used for documenting multiple property groups relating to one or several historic contexts. See instructions in How to Complete the Multiple Property Documentation Form (National Register Bulletin 16B). Complete each item by entering the requested information. For additional space, use continuation sheets (Form 10-900-a). Use a typewriter, word processor, or computer, to complete all items. New Submission XX Amended Submission A. Name of Multiple Property Listing Highway Bridges in Colorado B. Associated Historic Contexts The Historical and Technological Evolution of Colorado’s Bridges 1880 - 1958 Early Bridge Construction by the Railroads and Local Government Early Bridge Construction by the State Early Transcontinental Highways Depression-Era Bridge Construction Interstate Highways C. Form Prepared by name/title Clayton B. Fraser, Principal organization Fraserdesign date 30 March 2000 street & number 420 South County Road 23E telephone 970-669-7969 city or town Loveland state Colorado zip code 80537 D. Certification As the designated authority under the National Historic Preservation Act of 1966, I hereby certify that this documentation form meets the National Register documentation standards and sets forth requirements for listing of related properties consistent with the National Register criteria. This submission meets the procedural and professional requirements set forth in 36 CFR Part 60 and the Secretary of the Interior's Standards and Guidelines for Archaeology and Historic Preservation. (See continuation sheet for additional comments [ ].) State Historic Preservation Officer Signature and title of certifying official Date Office of Archaeology and Historic Preservation, Colorado Historical Society State or Federal agency and bureau I hereby certify that this multiple property documentation form has been approved by the National Register as a basis for evaluating related properties for listing in the National Register. Signature of the Keeper Date of Action Highway Bridges in Colorado Colorado Name of Multiple Property Listing State Table of Contents for Written Narrative Provide the following information on continuation sheets. Cite the letter and the title before each section of the narrative. Assign page numbers according to the instructions for continuation sheet in How to Complete the Multiple Property Documentation Form (National Register Bulletin 16B). Fill in page numbers for each section in the space below. page number E. Statement of Historic Contexts The Historical and Technological Evolution of Colorado’s Bridges 1880 - 1958 1. Introduction: Bridge Development in America................................................................... 1 2. Early Bridge Construction by the Railroads and Local Government.................................. 7 3. Early Bridge Construction by the State ........................................................................... 21 4. Early Transcontinental Highways.................................................................................... 33 5. Depression-Era Bridge Construction .............................................................................. 40 6. Interstate Highways........................................................................................................ 42 F. Associated Property Types Timber stringer and truss bridges............................................................................................. 62 Concrete slab and girder bridges ............................................................................................. 68 Concrete, stone, and steel arch bridges .................................................................................. 73 Concrete rigid frame bridges.................................................................................................... 83 Steel stringer and girder bridges ............................................................................................. 86 Iron and steel truss bridges...................................................................................................... 92 Glossary................................................................................................................................. 100 G. Geographical Data ............................................................................................................... 116 H. Summary of Identification and Evaluation Methods.......................................................... 117 (Discuss the methods used in developing the multiple property listing.) I. Major Bibliographical References....................................................................................... 118 State Historic Preservation Office, other State agency, Federal agency, local government, university, or other, specifying repository.) Primary location of additional data: [ ] State Historic Preservation Office [ ] Other State Agency [ ] Federal Agency [ ] Local Government [ ] University [X] Other Name of repository: Colorado Department of Transportation Paperwork Reduction Act Statement: This information is being collected for applications to the National Register of Historic Places to nominate properties for listing or determine eligibility for listing, to list properties, and to amend existing listings. Response to this request is required to obtain a benefit in accordance with the National Historic Preservation Act, as amended (16 U.S.C. 470 et seq.). Estimated Burden Statement: Public reporting burden for this form is estimated to average 120 hours per response including time for reviewing instructions, gathering and maintaining data, and completing and reviewing the form. Direct comments regarding this burden estimate or any aspect of this form to the Chief, Administrative Services Division, National Park Service, P.O. Box 37127, Washington, DC 20013-7127; and the Office of Management and Budget, Paperwork Reductions Projects (1024-0018), Washington, DC 20503. NPS Form 10-900-a OMB Approval No. 1024-0018 (8-86) United States Department of the Interior National Park Service National Register of Historic Places Continuation Sheet section number E page 1 H I G H W A Y B R I D G E S I N C O L O R A D O 1 Introduction: Bridge Development in America Bridges, as integral elements of a developing transportation network, have played a pivotal part in the development of America. Generally the most sophisticated components of any overland transportation system, they are also the most prominent. Not merely gauges of technological advancement in design and construction, bridges reflect the tenets, values, and ambitions of the people who erected them. “There can be little doubt that in many ways the story of bridgebuilding is the story of civilization,” Franklin Roosevelt stated in 1931. “By it we can readily measure an important part of a people’s progress.” While descriptive of the country in general, this was especially true for Colorado, a state in which overland transportation forms a central historical theme. From the earliest wooden spans put up during the first gold boom to the later iron and steel trusses erected on wagon roads and multiple-span urban viaducts for vehicular and tramway use, bridges have facilitated, and in some instances created, settlement across the state. A plethora of bridge forms, variously employing such materials as stone, timber, iron, steel, and concrete, were developed through centuries of empirical usage. By the time America was undergoing initial settlement on the East Coast, most of the principal bridge types and materials had been used or at least experimented with in other countries. What remained over the last two centuries has been a process of refinement revolving principally around the introduction and proliferation of structural metals and concrete as building materials. The first wooden bridges were merely plank structures—the equivalent of a log thrown across the stream. Limited in span to the wooden beam’s length and carrying capacity, they were used for only the shortest crossings. Without proper support, they became unduly strained by bending moment forces, leading to failure: the log broke. An advancement over this was the first significant bridge form in America, the pier bridge, also called the pike-and-beam bridge. Another ancient bridge type, it consisted of timber or log stringers spanning between timber pile bent piers, spaced at intervals of between 10 and 30 feet. In places where loose or shifting sediment proved unsuitable or was too deep for stone foundations, wooden piles were driven into the river to support the roadwork. A variation on the pile design, the crib bridge, used stacked logs for the piers. Timber stringer bridges were used extensively on the East Coast and further inland, as the settlement line moved westward. Consisting of multiple short spans of timber beams resting on pile bents or cribs, timber bridges were impractical across wide, deep rivers, and many were eventually replaced by timber trusses in the late 18th century. Nonetheless, timber stringer bridges continue to be the most commonly built vehicular bridge type, one that continues to be built for minor crossings. The use of stone as a building material was also transferred to America from Europe. Long known for its compressive strength, stone (or more specifically the mortar