William Jennings graduated from Southern Illinois University and studied law at Union College of Law in Chicago. He relocated to Florida, where he held various judicial and political roles, including county judge and Speaker of the Florida House of Representatives. Jennings was elected governor in 1900, during which he introduced significant reforms such as the statewide primary election system and proposed the draining and development of the Everglades. After his governorship, he established a law practice in Jacksonville and continued to engage in public service.

William Jennings combines a progressive approach to electoral democracy with a bold vision for environmental transformation. His introduction of the statewide primary election system in 1902 reveals a commitment to democratizing political participation. However, his proposal to drain and develop the Everglades juxtaposes this progressive stance with an aggressive interventionist policy, showcasing an unusual blend of environmental and economic pragmatism. Jennings's tenure as general counsel for the Internal Improvement Fund further highlights his dedication to large-scale public works projects, balancing his regional influence with ambitious state-level initiatives.