Hadley was born in Cincinnati, Ohio, and raised in Toledo. He worked as a surveyor in North Dakota, and came west as part of the U.S. Coast & Geodetic Survey. Before settling in Seattle, he worked on a surveyor crew for the Great Northern Railroad, Copper River Railroad in Alaska, and for the Canadian Northern Railroad in Vancouver. He studied engineering intermittently at the University of Washington, attaining the equivalent of about three years of study.
Hadley was experienced in building concrete ships and barges in Philadelphia during World War I for the Emergency Fleet Corporation. As would happen during and after World War II, steel shortages forced the Government to seek alternate sources of materials for use in shipbuilding. In 1920, as a young engineer working in the architectural office of the Seattle School District, Hadley suggested a floating bridge across Lake Washington, supported by concrete pontoons.
Hadley formally proposed his idea at a meeting of the American Society of Civil Engineers on October 1, 1921. Hadley's proposal caused considerable debate. Skeptics included Seattle civic leaders, The Seattle Times, and the Lake Washington Protective Association. Even the Navy, with its station at Sand Point, opposed the idea, citing aesthetic considerations. He had hoped to build the bridge as a toll bridge with private money, but bankers ridiculed the idea, calling it "Hadley's Folly."
In 1921, Hadley took a job with the Portland Cement Association, promoting the increased use of cement for large-scale projects. He was sent to Japan in 1923 after the Great Kanto earthquake to study the effects on different types of structures.
Hadley continued to dream about the creation of the bridge for the next 10 years. While highly critical of Franklin Roosevelt's politics, he nonetheless went to see Lacey V. Morrow (brother of famous radio and television journalist, Edward R. Murrow), director of the State Department of Highways, when federal monies became available to the states in the depth of the Great Depression. Murrow was intrigued by the concept and his staff verified that the design was feasible.
In the mid-1930s, Homer Hadley designed one of the first paving machines in the United States. At the time, a prototype laid a strip of pavement on the highway to Orting, Washington.
In the 1930s Hadley had also become well established with the Portland Cement Association, a fact that caused Murrow to encourage Hadley to step out of the limelight of the floating bridge project, now underway. Murrow was concerned that the Association's motto, "to extend and promote the uses of concrete," would cause the opposition factions to paint Hadley as having ulterior motives for promoting his design. Murrow assured Hadley that he would be given credit for his contribution -- a promise he was not to keep.
A biography of Homer Hadley, written by his son Richard (d. 2002) in 1967, claims that Homer Hadley designed the first concrete box-girder bridge in the United States. The bridge cited is the Mashall Bridge (Pierce County Bridge #24164-A) near Eatonville. Further research may be required to verify this claim, based on a letter from Homer Hadley to Pierce County road engineer, Keith Jones. The letter is dated September 10, 1962, and in it Hadley himself addresses the issue by stating, "which I believe is the first concrete box-girder bridge in the United States."
Hadley's floating bridge design was in response to Seattle's immensely challenging water barrier to the east of the city -- deep, glacially carved Lake Washington. The design of the Mercer Island Bridge (also called Lake Washington Floating Bridge) was considered radical, but was approved in 1937, and opened in 1940 to rave reviews.
The bridge paved the way for development of the Eastside. In 1967, the bridge was renamed after Lacey V. Murrow. In 1993, Seattle's Mortar Board Alumni (University of Washington) led a successful statewide effort to name the newest Lake Washington floating bridge for Homer Hadley. The campaign was unanimously approved by the state legislature.
Similar designs were utilized for other floating bridges to come. In 1963, the second floating bridge across Lake Washington was opened. The Evergreen Point Bridge carries Route 520 from Montlake to Evergreen Point. In 1961, the Hood Canal Bridge opened, carrying Route 104 from the Olympic Peninsula to the Kingston ferry landing, bridging Jefferson and Kitsap counties. The latest floating bridge, running parallel to the original was opened in 1989, and named for Homer Hadley.
Giving up a lifelong pension within only four years of retirement, Homer Hadley struck out on his own as a private engineering consultant in 1947. His son Richard joined him soon thereafter, and the pair designed several buildings in Juneau, Alaska, in the late 1950s and early 1960s. Hadley had brought his experience of Kanto to bear, and all his buildings survived the Alaska earthquake of 1964, which measured 9.4 on the Richter scale.
As a member of the Earthquake Committee, Seattle Section, American Society of Civil Engineers (ASCE), Hadley participated in reporting and making recommendations on the 1949 Pacific Northwest earthquake.
In 1955, Hadley designed a bridge that would set a national precedent. Hadley described the design initially as a "tied-cantilever" but the significance would be recognized later as it became a prototype for what would be called "cable-stayed" bridges. This is a bridge in which the superstructure is supported by cables or stays attached to a tower or towers located at the main pier(s).
Moving into the design of steel bridges later in his career, Hadley designed the Parker River Bridge, which was erected over the Yakima River between Benton City and Kiona. In 1962, the Iron and Steel Institute (AISC) awarded the bridge First Prize for "the most beautiful bridge of its class in the United States." His steel "delta girders" were the subject of the feature article in the May 1966 issue of Civil Engineering.
Homer M. Hadley worked up until his death in July 1967. He died unexpectedly at his summer home at Soap Lake.