William Hinckle Smith was born on June 16, 1861 in Philadelphia, Pennsylvania. He attended the University of Pennsylvania's Towne Scientific School (now the School of Engineering and Applied Sciences) from 1881-1882. Smith married Jacqueline Harrison on November 28, 1882 and the couple had one son, Hoxie Harrison Smith (b. 1887), a veteran of the First World War.

Smith was the owner of the Wanotan Ranch, a 6,000 acre farmstead in Amenia, North Dakota. The wealthy broker and financier also had a close association with the Guggenheim copper interests, where he derived most of his wealth. Smith also directed the Girard Trust, Penn Mutual Life, Baldwin Locomotive, Midvale Steel, Mack Truck, and the Curtiss-Write Corporation. Outside of Pennsylvania, Smith operated shares with other companies, including L.E. Newport Incorporation (New York City, NY), International Bitumenoil Corporation (New York City, NY), and the Tonopah-Aspen Mining Company (Tonopah, NV/Aspen, CO). The capitalist was also a charitable man; he was a patron of the University of Pennsylvania's University Museum, the Pennsylvania Horticultural Society, and the Bryn Mawr Hospital (which he served on the board from 1906-1943, longer than any other board president), as well as a trustee of the University of Pennsylvania and Fairmount Park Art Association.

In 1907, Smith enlisted architect Charles A. Platt to design his home, a massive 60-room mansion called Timberline, in Bryn Mawr, Pennsylvania. Here, Smith maintained meticulously groomed landscapes (designed by the Olmsted Brothers) and stables, as he was an enthusiastic horseman. Upon Smith's death on January 28, 1943, Timberline passed to his heirs, who, after only three years, lost interest in the mansion. The home succumbed to deterioration and was eventually demolished in 1977.