Starkweather enlisted in the 23rd United States Engineers in World War I, and served in France as a French‑trained artillery officer. He rose to the rank of second lieutenant and later became a charter member of the Morgan‑McDermott Post of the American Legion.
Returning to Tucson in 1919 following the war, he brought back the blueprint company. He married Otilia E. Jettinghof in 1921 and was politically active throughout the early 1920s. He was elected to the Tucson City Council in 1924 and serving as the president of the Board of Health in 1926.
In the late 1920s he was hired as the overseeing architect of El Encanto Estates, and designed sixteen elegant and formal houses in the development.
Starkweather founded the Arizona chapter of he American Institute of Architects in 1937 and was named a Fellow in 1968 for his public service. Starkweather was also a charter member of the Tucson Kiwanis Club. He also served in the Elks Club as exalted ruler, state president and grand lodge officer. In addition, he was a thirty‑third degree Mason.
With Sheriff Ed Echols, Starkweather founded the Tucson Rodeo and designed the original arena and the rodeo facilities on South Sixth Avenue. He was also rodeo chairman from 1944 to 1946.
In 1945 Starkweather partnered with Richard A. Morse to create a new firm. In 1946 he served as chairman of the city zoning commission for eleven years and sold the blue print company again in 1947.
Starkweather designed several landmark buildings throughout Tucson including: Carrillo, Drachman, Bonillas, and Doolen Junior High Schools; the Tucson High School Stadium; St. Joseph’s Academy, a Saint Mary’s Hospital addition and convent.
Arguably, his most significant and enduring work was the design of the nationally famous Arizona Inn under the patronage of Isabella Greenway.
Other major Arizona buildings included Women’s Club in Safford, Arizona; the Elk’s Lodge in Nogales, Arizona and the Casa Grande Hospital.
Merritt Howard Starkweather died in 1972 and the age of 81.