On May 15th, 1829 Joseph Smith and Oliver Cowdrey went into the woods to pray about the authority to baptize. They were inspired to ask while translating The Book of Mormon, as they came across verses describing God’s authority to perform sacred works. Their prayer was answered, and John the Baptist visited Joseph and Oliver and gave them the Aaronic Priesthood.
Though popular belief holds that the restoration took place directly on the banks of the Susquehanna River, historical research reveals a more likely scenario. Due to geographical constraints during 1829, Joseph and Oliver likely found a secluded area of wood on Joseph’s property in Palmyra, New York. This would have been near, but not on the banks of the Susquehanna River. Later in the day, they would return to the river itself and baptize each other, exercising the newly restored priesthood for the first time in the latter-days.
For more information on the restoration of the Aaronic Priesthood watch this short historical video.