The Hillsborough River is a river located in the state of Florida in the United States. It arises in the Green Swamp near the juncture of Hillsborough, Pasco and Polk counties, and flows through Pasco and Hillsborough Counties to an outlet in the city of Tampa on Hillsborough Bay. It includes 4 nature trails extending for over , making it perfect for hikers. The name Hillsborough River first appeared on a British map in 1769. At the time, the Earl of Hillsborough was the British Secretary of State for the Colonies, and thus controlled the pensions of the surveyors working in the American colonies, which included East Florida. History Geological data estimates that the Hillsborough River has been flowing for about 27,000 years. It is estimated humans first made their way to this area 12,000 - 15,000 years ago. In the late 18th century the watershed of the Hillsborough River was a land covered by a rich, old-growth forest. Majestic bald cypress, longleaf pine, and sand live oak were hundreds of years old (and in the case of cypress, thousands of years old). In the mid to late 19th century to about 1913 the watershed of this old growth forest began to be logged. As a result of this lumbering activity, most of the trees within the Hillsborough River basin are now less than 100 years in age. The harvesting of the old growth trees altered the ecosystems they dominated. Trees such as water ash and water locust were able to quickly grow in the sun-lit spaces created when bigger trees were removed. The riverine swamp forest as it exists today has a much different ecology than the ecosystem that had existed along the Hillsborough for the previous ten to 15,000 years. When Europeans first reached Florida, the area around Tampa Bay and all of the watershed of the Hillsborough River was occupied by people of the Safety Harbor culture. Two chiefdoms of the Safety Harbor culture, Mocoso and Pohoy, were adjacent to where the Hillsborough River entered Tampa Bay. Hernando de Soto landed on the south side of Tampa Bay in 1539 and passed through Mocoso on his way north. By the early 18th century the people of the Safety Harbor culture, through disease and slavery, are nearly exterminated. Timeline (1757) A survey of the Hillsborough River is done by Don Francisco Maria Celi, pilot of the Spanish Royal