Reginald Heber Thomson (1856-1949), a Seattle civil engineer, official, and consultant, is credited with establishing much of the municipal infrastructure of the fledgling city of Seattle. Thomson was Seattle city engineer from 1892 through 1911 and again in 1930 and 1931. He chaired the Seattle Public Works Board 1896-1911, established the Port of Seattle in 1911, served as superintendent of Stathcona Park, Vancouver Island, from 1912 to 1915, and was a member of the Seattle City Council from 1916 to 1922. Thomson consulted on major water and hydroelectric projects in Washington, Oregon, British Columbia, and Alaska. Among the many projects he is known for are several major regrades of Seattle's business district and waterfront, the establishment of Seattle's first hydroelectic plants, and establishment of the Cedar River water supply and the West Point sewage treatment plant.

Early in his career, Thomson entered into a partnership with F. H. Whitworth, the city and county surveyor. One of Thomson's early tasks as assistant surveyor involved the initial work of dredging a canal between Lake Washington and Lake Union where, decades later, he would be instrumental in constructing the Lake Washington Ship Canal connecting both lakes to Puget Sound. In 1884, Thomson became the city surveyor. In this role he built Seattle's first sewers and the Grant Street bridge across the tideflats. He resigned in 1886 to work for the Seattle, Lake Shore & Eastern railroad. As locating engineer, he plotted the path of the railbed from the northern end of Lake Washington all the way eastward through Snoqualmie Pass, to Lake Keechelus. Not stopping there, he moved on to Spokane for a few years where he constructed terminals and built two bridges. Once back in Seattle, he worked as a consulting engineer. Then, in 1892 he became city engineer, a job that he would hold for the next 20 years. He added 4.5 miles of sewer lines throughout the city, much of it through formations that had stymied earlier engineers. He also worked on creating the growing community's first sidewalks and paved roads, including Lake Washington Boulevard, which he and his assistant, George F. Cotterill (1865-1958), first designed as a cinder path for bicycles.

His first regrade, in 1898, was up 1st Avenue from Pike Street to Denny Way. Five years later, Pike and Pine were regraded from 2nd Avenue to Broadway. For the next eight years, Thomson's crews pummeled Denny Hill, between 2nd and 5th Avenues, and Pike Street and Denny Way. Thomson also went after the hillock between Main and Judkins Streets and 4th and 12th Avenues. Dearborn Street was regraded, and the 12th Avenue Bridge was built to Beacon hill. He created Westlake Avenue, which provided level access to Lake Union. In all, Seattle regraded 25 miles of streets, which displaced 16 million cubic yards of dirt. This dirt was poured into the tideflats south of the city, the landfill creating a whole new industrial section for the burgeoning metropolis. When James J. Hill (1838-1916), owner of the Great Northern Railroad, established his terminus in Seattle, Thomson convinced him to bypass the waterfront's already crowded Railroad Avenue (now Alaskan Way) and establish King Street Station south of Pioneer Square. Thomson had a tunnel built beneath the city from Virginia to Washington Streets, which was completed in 1906.

Seattle used to get water from a reservoir on Beacon Hill filled with water pumped from Lake Washington, but as the city grew, this system became woefully inadequate. Thomson looked towards the Cedar River Watershed as a source of freshwater for Seattle residents, located 30 miles southeast of Seattle in the foothills of the Cascade mountain range. By 1899, work on the pipeline had begun in earnest. On December 24, 1900, a test was made of the water flow to look for leaks. The system worked well enough that on January 10, 1901, water began flowing into the Volunteer Park reservoir in Seattle. More than a century later, Seattle and King County still use the Cedar River watershed.

Thomson and his crew designed and built the City Light Cedar Falls hydroelectric plant, which went into operation on October 4, 1904. On January 10, 1905, electric current illuminated streetlights in Seattle, and by September 9, City Light began serving private customers, which it does to this day. At the urging of the city council, Thomson was asked to take a well-deserved vacation from all of his good work. He visited Europe, where he "made examination of nearly everything connected with city life, such as water, lights, sewers, conditions accelerating city growth, cities' fire control, municipal baths, municipal laundries, and so forth."

From 1905 to 1915 Thomson also became president of the University of Washington's board of managers. During this time he also examined the flow of commerce along Seattle's waterways. This interested him so much, that he resigned as city engineer in 1911 to organize the Port of Seattle, established largely through his efforts at lobbying the state legislature. Under Thomson's direction as engineer, the Port Commission made far reaching developmental plans, many of which are still in effect. While on the commission, Thomson pushed for acquisition of Smith Cove and the foot of Bell Street for use by the Port. He advocated deepening and straightening the Duwamish River for use in the industrial area, and also campaigned in Washington D.C., for funds to build the Hiram M. Chittenden Locks.

From 1916 to 1922, he was a member of the Seattle City Council, yet he continued to do engineering work. He was a consultant on the Rogue River Valley Irrigation canal, and built a hydroelectric plant in Eugene, Oregon. He was in charge of water development in Bellingham. He surveyed power-plant sites in Southeastern Alaska. He returned, temporarily, to his job as Seattle city engineer in 1930 to oversee the final work on the Diablo Dam on the Skagit River. After that, he was a consulting engineer for both the Wenatchee Metropolitan Water System and the Inter-County River Improvement Commission for Pierce and King counties. He also consulted on the construction of the Lake Washington Floating Bridge and for the foundations of the Tacoma Narrows Bridge. Reginald Thomson died on January 7, 1949, at the age of 92. Immediately prior to his death, he wrote his autobiography, That Man Thomson (published posthumously).