As part of this effort, Fort Brooke was established on January 10, 1824 by Colonels George Mercer Brooke and James Gadsden at the mouth of the Hillsborough River on Tampa Bay, just about where today's Tampa Convention Center sits downtown. The site was marked by a huge hickory tree set atop an ancient Indian mound most likely built by the Tocobaga centuries before. Brooke, the outpost's first commander, directed his troops to clear the area for the construction of a wooden fort and support buildings, but ordered that several ancient live oak trees inside the encampment be spared to provide shade and cheer. On January 22, 1824, the post was officially named Fort Brooke. John Mercer Brooke was born there. The first post office was established in 1831.