Harmon and his uncle both liked the idea; together they pooled a total of $3000 to start Wood, Harmon & Co.

Their first development was near Loveland, Ohio, and consisted of 200 lots. With some well-crafted advertising, the development sold out in 4 days. Further developments were soon built in Ohio and western Pennsylvania, followed by expansion into various cities in the Midwest and the East Coast of the United States. Harmon relocated to Pittsburgh around 1891, then to Philadelphia in 1895. Wood, Harmon & Co. soon had offices in over 26 cities.

In 1900 Wood, Harmon & Co, purchased large tracts of land in Brooklyn, New York, in anticipation that the building of the Brooklyn Bridge and expansion of the city's rail transit would provide opportunities for the company. The bet on this expansion proved to be fortuitous, with the company ultimately developing over 20,000 building lots in Brooklyn. Wood, Harmon & Co. also diversified by creating other companies to acquire and hold business properties and real estate for lease and/or sale.

In 1907, disagreements between the partners resulted in the dissolution of Wood, Harmon, & Co., with Clifford Harmon forming his own development company. Harmon had already taken the lead in developing several properties in the New York metropolitan area, notably Pelhamwood starting around 1909 and continuing to develop Harmon-on-Hudson (now part of Croton-on-Hudson), initially developed in 1903 as an artists colony. He also continued with real-estate development in other cities such as Philadelphia, such as the development of Penfield in Haverford, and Louisville, Kentucky. The Clifford B. Harmon & Co. continued to advertise until around 1930, after which the firm presumably closed.