All public lands and buildings, not including harbor areas and navigable streams and bodies of water and the submerged lands underlying the same, owned by the United States in the island of Puerto Rico and not reserved by the President of the United States prior to July 1, 1903, pursuant to authority vested in him by law, are granted to the government of Puerto Rico, to be held or disposed of for the use and benefit of the people of said island. Said grant is upon the express condition that the government of Puerto Rico, by proper authority, release to the United States any interest or claim it may have in or upon the lands or buildings reserved by the President as mentioned herein. Nothing herein contained shall be so construed as to affect any legal or equitable rights acquired by the government of Puerto Rico or by any other party, under any contract, lease, or license made by the United States authorities prior to the 1st day of May 1900.