Born in Iowa on January 10, 1870, Thomas came to architecture from an interest in science, mechanics, and drawing. Before entering Colorado State College, he was a carpenter, which led to drafting work for an architecture office in Denver. While in college, he designed a house and two campus buildings.
Thomas spent the next decade enhancing his technical background with extensive European travel and study. During his first sixteen-month trip, Thomas studied in a Parisian studio. After a brief return to his Denver practice, Thomas traveled around the world, sketching what he saw, compiling a library of ideas that informed his life’s work.
In 1906, after years of travel, Thomas settled down in Seattle. By 1907, he was designing two Seattle hotels, the Chelsea and the Sorrento. The Sorrento, at 900 Madison Street, is an eclectic building, illustrating a number of stylistic details uncommon in Seattle in the 1910s.
By contemporary standards, the Sorrento was unusual and fantastic. Its ell-shaped floorplan opens to the street’s corner, creating an open park-like space. Rather than a building entry through a single, central door or a streetside entrance, Thomas’s design provides a civilized, intermediate landscape, separating the public life of the street from the building’s private interior spaces. The symmetrical flanking wings draw the visitor and the eye to the central entrance.
Although the many details of the building's recessed facade enrich the exterior’s surfaces, the building’s roofline is one of its most striking features. Thomas added interest to the roof with pergolas, which are open, Italian-influenced elements, often found in garden walkways.
The Sorrento provided Seattle with its first rooftop restaurant.
In the first years of his Seattle practice, Thomas designed a number of regional schools including:
- J. M. Weathermax High School, Aberdeen (1908-1909; altered)
- Monroe High School, Monroe (1909-1910; destroyed)
- The Enumclaw High School, Enumclaw (1910-1911; destroyed)
Thomas worked in partnership with several local firms throughout his career. Most of his designs were collaborative efforts. Examples of these, and associated firms are:
- The Corner Market Building (1911-1912, with Clyde Grainger)
- The Queen Anne Branch of the Seattle Public Library (1912-1914, with W. Marbury Somervell)
- The Henry L. Yesler Library (1912-1914, now the Douglass-Truth Library, with W. Marbury Somervell)
- The Seattle Chamber of Commerce Building (1923-1925; altered, with Schack, Young & Myers)
- The Sales and Service Building (1925, as a part of Thomas, Grainger & Thomas)
- Rhodes Department Store (1926-1927, now the Arcade Plaza Building, as a part of Thomas, Grainger & Thomas)
- Harborview Hospital (1929-1931, altered, as a part of Thomas, Grainger & Thomas).
In addition, he designed his personal residence, a few fraternity and sorority buildings, as well as speculative housing in northeast Seattle for Albert Balch. During World War II, Thomas designed a 500-unit housing project in Bremerton with Smith, Carroll & Johanson.
Thomas also advanced the field of architecture locally as an active member of the American Institute of Architects (AIA), and as a faculty member with the University of Washington’s architecture department. From 1926 to 1940, he served as department chair.
Thomas retired from architectural practice in 1949, but continued expanding his experience. Late in life, he became a respected painter. He died on September 4, 1953, leaving Seattle’s architectural community a substantial legacy.