Treaty of Washington (1900)

The Treaty of Washington of 1900 was signed on November 7, 1900, and came into effect on March 23, 1901, when the ratifications were exchanged. The treaty sought to remove any ground of misunderstanding growing out of the interpretation of Article III of the 1898 Treaty of Paris by clarifying specifics of territories relinquished to the United States by Spain. It explicitly provided:

"Spain relinquishes to the United States all title and claim of title, which she may have had at the time of the conclusion of the Treaty of Peace of Paris, to any and all islands belonging to the Philippine Archipelago, lying outside the lines described in Article III of that Treaty and particularly to the islands of Cagayan [Mapun], Sulu and Sibutu and their dependencies, and agrees that all such islands shall be comprehended in the cession of the Archipelago as fully as if they had been expressly included within those lines."

In consideration for that explicit statement of relinquishment, the United States agreed to pay to Spain the sum of one hundred thousand dollars ($100,000) within six months after the exchange of ratification. The Treaty of Washington is also known as the Cession Treaty.

The treaty has been cited by the Filipino legal community as a supporting basis for the Philippine sovereignty over the disputed Scarborough Shoal and Spratly Islands in the South China Sea. According to former Associate Justice Antonio Carpio, the treaty amended the 1898 Treaty of Paris by including several islands outside of the bounds of the 1898 treaty still under Spanish possession, citing three maps published during the Spanish colonial era which included the two disputed areas as part of the Philippine territory. Both the 1898 and 1900 treaties were incorporated in the first article of the 1935 Constitution of the Philippines concerning the scope of the national territory.