Short answers, pulled from the story.
The Diomede Islands are located in the middle of the Bering Strait, between mainland Alaska and Siberia. Big Diomede belongs to Russia and Little Diomede belongs to the United States. The two islands are approximately 3.8 km apart at their closest points.
The International Date Line passes between the two islands, making Big Diomede 21 hours ahead of Little Diomede (20 hours in summer). This time difference gave rise to the nicknames Tomorrow Island for Big Diomede and Yesterday Island for Little Diomede.
Danish-born Russian navigator Vitus Bering sighted the islands on the 16th of August 1728 (old style calendar). He named them after Saint Diomedes because that date is when the Russian Orthodox Church celebrates the memory of the saint.
After the Soviet government established a military base on Big Diomede in 1948, it relocated the island's indigenous population to mainland Russia. The island has been inhabited only by military units ever since.
During the Cold War, the narrow channel between Big Diomede (Soviet Union) and Little Diomede (United States) became known as the Ice Curtain. In 1987, swimmer Lynne Cox crossed from one island to the other, earning congratulations from both Mikhail Gorbachev and Ronald Reagan.
Little Diomede had an Inupiat population that declined to 115 at the 2010 census. All residents live in the village of Diomede on the west side of the island, which has a school, a post office, and a store.