On what date did Alaska's transfer from Russia to the United States become effective in 1867?

Alaska's transfer from Russia to the United States became effective on October 18, 1867.

The United States and Russia signed the purchase treaty on March 30, 1867, and the U.S. Senate ratified it on May 15. The formal transfer ceremony took place in Sitka on October 18, when Russian troops lowered their flag and American troops raised theirs.

The United States paid Russia $7.2 million for Alaska, a price of roughly two cents per acre at the time. Secretary of State William H. Seward negotiated the agreement for President Andrew Johnson's administration.

Some critics called the purchase “Seward's Folly” or “Seward's Icebox,” believing the territory was useless. Alaska later became a U.S. territory in 1912 and a state in 1959.