In 1881, Lakota leader Sitting Bull surrendered to federal troops. In 1944, President Franklin Delano Roosevelt won the Democratic presidential nomination for the fourth and final time. In 1969, Neil Armstrong, commander of Apollo 11, became the first person to set foot on the Moon, followed by Buzz Aldrin. In 1976, Viking 1 landed on Mars and transmitted the first photos of the planet's surface. In 2015, the U.S. and Cuba reopened embassies in their respective countries, formally reestablishing diplomatic relations for the first time since 1961.