By Allan King Sloan

Prepared for the Historic Bridge Association Newsletter,  May, 2006

Zenas King founded the King Iron Bridge Company in 1858 and it built iron and steel bridges all over North America for the next six decades. In the 1860s and 70s, the company’s main product was a bowstring truss bridge patented by Zenas in 1867 for which it received contracts first in Ohio, then throughout the East, Midwest, Southwest and Mountain States. The bowstring was an extremely popular and efficient way of bridging small rivers and streams with prefabricated sections manufactured in King’s Cleveland factory and shipped by rail to building sites where a local crews could put up a structure in a few days. The company was invited to erect one of their bowstrings for the centennial celebration in Philadelphia in 1876, which was used extensively in subsequent publicity.

By the early 1880s production was focused on larger and heavier standard American Standard (Pratt) trusses as well as swing bridges, for which Zenas had received another patent in 1867. The company’s sales agents were entrenched in almost every state in the union, as well as in Canada. The Cleveland factory was producing at a rate of about 200 bridges a year, making it one of the largest iron bridge builders in the nation.

By the late in the 1880s, the company was in a position to help Zenas realize his dream of becoming the designer and builder of major river crossings using the latest in advanced bridge technology. It was one of the first of the large independent bridge manufacturers to specialize in cantilever bridges, and built the Central Bridge across the Ohio River between Cincinnati and Newport, Kentucky, (just east of Roebling’s suspension bridge), the Willamette River Bridge in Albany, Oregon, and the Youghiogheny River Bridge at Boston, Pennsylvania.

It also built the Grand Street Viaduct, a well admired suspension bridge in St. Louis and the Cedar Avenue Bridge in Baltimore, noted for its innovative spandrel design. The company built three notable swing bridges across the Chicago River that helped spur the development of Chicago’s famous loop. It also helped build two swing bridges across the Harlem River in New York City, the first a highway bridge designed by the famous bridge designer, Albert Boller, and the second, a four track bridge for the New York, New Haven and Hartford Railroad known as the Park Avenue bridge that was used until 1954.

One of its major engineering achievements was the design and construction in 1888 of the much celebrated Central Viaduct in Cleveland, a two branch structure of over 4,000 feet across the Cuyahoga River Valley with a central moveable span. And to top Zenas’s ambition, in 1892 he and some business colleagues had a bill introduced in the New York State Assembly for a franchise to build two major bridges across the East River in New York City in locations now occupied by the Queensboro Bridge and the Triboro Bridge. Zenas died in 1892 and with him his grand plan.

After Zenas died, the King Bridge Company continued to prosper under the leadership of first, his eldest son, James A. King and later his youngest son, Harry W. King, along with a group of very talented engineers. In addition to standard Pratt and Pennsylvania trusses, the company produced a variety of moveable bridges; swings, bascules, and retractile, plus spandrels, viaducts and unspectacular beam girders for both highway and railroad use, many featuring multiple spans across important rivers. Much of the work in this era was done in collaboration with other companies. By the late 1890s the company claimed to have built over 10,000 bridges.

In the era when the American Bridge Company under the guidance of financiers Andrew Carnegie and J.P. Morgan was acquiring the King Bridge Company’s major competitors, the Kings resisted a buyout and continued the company as a family owned enterprise. Despite trouble with anti-trust laws and a rapidly restructuring iron and steel industry, the company was able to survive until 1922. Its last major structure was the center span of Cleveland’s Veteran Memorial (Detroit-Superior) Bridge which was built during World War I and still stands today as an important civic landmark.


Most of the great bridges built by the King Bridge Company have long since disappeared under pressure from growth of highway traffic and the demise of many of the nation’s railroads. The Veteran’s Memorial Bridge is the only one of the major structures still in use for high volume traffic and has been rehabilitated to last many more years. A number of solid beam girder bridges bearing the King Bridge Company builders plate still serve operating railroads. There are a few moveable bridges still standing, most notably the Center Street Swing Bridge in Cleveland which still performs as originally designed and

The University Heights Bridge in New York City, which started life as the swing bridge across the Harlem Ship Canal in 1896, was removed to a new location in 1903 and still carries traffic after years of tender, loving care. “OLD NAN”, a bascule bridge across the Niantic River in Connecticut on the main rail line between Boston and New York built by King and the Scherzer Lift Bridge Company in 1907 is still used by AMTRAK, but its days are numbered. The HOJACK Bridge in Rochester, New York, the last or the King railroad swing bridges, is still standing but under orders for removal by the U.S. Coast Guard, for it is no longer in use for transportation.

The Historic American Engineering Record (HAER) includes 30 King bridges in its historic bridge inventory, second only to the American Bridge Company in the number of bridges so listed. Most of these no longer exist, but at least six are still standing.

Most remaining King bridges have escaped destruction because of the dedication of enlightened owners and historic preservationists. To date we have been able to identify about 75 of these in locations from Nova Scotia to Mexico. Most are early bowstrings and standard trusses which have either been rehabilitated to carry light vehicular traffic or used on biking and hiking trails in local parks or pedestrian crossings of rivers and streams. One of those preserved, the Fort Laramie Army Bridge, a King bowstring built in 1876, is actually owned and maintained by the U.S. Government (the NPS).

The Fort Laramie Army Bridge

Most of the rest are owned by county or town governments or private individuals who have acquired the structure for one reason or another. More and more, local historical societies and old bridge enthusiasts are mobilizing to pressure local and state governments to save these old bridges as important pieces of their local history and heritage. At present, there are at least 8 projects underway or pending to preserve old King Bridges (including the Hale Bridge in Jones County, Iowa, the Black Warrior Bridge in Northport, Alabama and the Bullman bowstring in Hamilton County Texas) and 8 more have been completed in the last three years (including the Alton Bridge in Denton County, Texas). A list of these can be found on the King Bridge Company Museum website ( in the Preservation Section.

In addition, a number of other notable King Bridges have been kept in tact for either local traffic service or for recreational use. Among these are: The Faust Street Bridge in New Braunfels, Texas, the 2nd Street Bridge in Allegan, Michigan, the Wabash Cannonball Bridge in St. Francisville, Illinois, the Rosendale Viaduct in Ulster County, New York, the “New” Bridge in River Edge, New Jersey, the Dearborn River Bridge near Augusta, Montana, the “Singing Bridge” in Frankfurt, Kentucky, the Moores Crossing Bridge in Travis County, Texas, the Belmar Bridge in Venango County, Pennsylvania, the Merriam Street Bridge in Minneapolis, and the Casino Bridge on Belle Isle, Detroit.

If the reader has any information on old King bridges, please contact the website noted above.

About the Author:

Allan King Sloan is the great-grandson of James A. King whose father, Zenas, founded the King Bridge Company in 1858. He is a city planner who specialized in transportation and urban development issues over a 40 year career that involved work in New York City, Boston, Philadelphia and other regions in the U.S.A., Europe and the Middle East. He was a vice-president of Arthur D. Little International, the management consulting firm, from which he retired in 1995.Since then he has been active in efforts to preserve historic bridges, including Kings.

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