The Interlachen Bridge is historically significant as an outstanding, virtually unaltered, early example of a reinforced concrete arch bridge employing the patented Melan reinforcing system in Minnesota. Built in 1900 by William S. Hewett, it is the earliest known extant concrete bridge in Minnesota with a documented construction date. The Interlachen Bridge is one of the most significant bridges in Minnesota.
The I-beam, arch-reinforcing-system invented by the Viennese engineer Josef Melan was patented in the United States in 1894. The first Melan-system bridge was built in Rock Rapids, Iowa, that same year. The contractor who built that first Melan bridge was William S. Hewett and Company of Minneapolis. When the Twin City Rapid Transit Company embarked on electrification and expansion in the 1890s and into the early 20th century, Hewett designed and built all the bridges required by the system on a cost-plus basis.
A bridge was declared necessary between lakes Calhoun and Harriet because of the anticipated heavy traffic which the existing roadway was not wide enough to accommodate. In 1899, the Minneapolis Board of Park Commissioners appropriated $5,000 for the new bridge over the street railway tracks and the contract for the bridge was let late in the season to William S. Hewett. The contractor completed work on the abutments in 1899 and finished the bridge's superstructure in 1900. On August 6, 1900, the Board's Standing Committee on Improvements reported that they have examined the bridge constructed by W.S. Hewett and was accepted. The final cost of the bridge was $6,900.
William's son, Maurice, has written in an unpublished biography of his father that "one of the very early Melan type arch bridges built in this country was the bridge planned and built by Mr. Hewitt carrying the parkway between Lake Calhoun and Lake Harriet over the street railway tracks." Four years later, in 1904, William S. Hewett and Company was the contractor for Bridge No. 92247 in St. Paul's Como Park. Except for minor differences in some dimensions, the bridge is virtually identical to the Interlachen Bridge. Bridge No. 92247 is thoroughly documented in engineering literature as a Hewett-built, Melan-system bridge. This evidence strongly supports Maurice Hewett's statement that the Interlachen Bridge was built on the Melan system.
Contractor William S. Hewett (1864-1951) is significant as a major Minneapolis bridge builder from the 1890s until well into the 20th century. He is further significant for his pioneering work in reinforced and pre-stressed concrete. Hewett probably became familiar with the Melan reinforcing system when he built the first American Melan bridge while he was doing general bridge construction in northwest Iowa. At the time he was an agent for his uncle, Seth M. Hewett. In 1899, he formed his own William S. Hewett and Company, specializing in reinforced concrete bridges, and it was this firm that built bridges 92247 and L-5853 in St. Paul in 1904. In 1907, he formed the Security Bridge Company and in 1913, Hewett Systems, after which he focused on the development of pre-stressed concrete.