 In 1907 another former classmate John Zimmerman joined the firm as partner, and they renamed the firm Dodge, Day & Zimmermann.After Kern Dodge withdrew as partner in 1911 the firm became Day & Zimmermann, incorporated in 1916,

In its early years the company came into prominence with the design of the construction of the Gatun Lock System, one of the Panama Canal locks in 1907.The construction of the Gatun Lock began with the first concrete laid at Gatun, on August 24, 1909, by Day & Zimmermann.