The Buenos Aires Metro, the first underground railway system in the Southern Hemisphere and in Latin America, begins operation.

The Buenos Aires Underground, locally known as Subte, is a rapid transit system that serves the area of the city of Buenos Aires, Argentina. The first section of this network opened in 1913, making it the 13th earliest subway network in the world and the first underground railway in Latin America, the Southern Hemisphere, and the Spanish-speaking world, with the Madrid Metro opening nearly six years later, in 1919. As of 2024, Buenos Aires is the only Argentine city with a metro system.

The Southern Hemisphere is the half (hemisphere) of Earth that is south of the equator. It contains all or part of five continents and four oceans, as well as New Zealand and most of the Pacific Islands in Oceania. Its surface is 80.9% water, compared with 60.7% water in the Northern Hemisphere, and it contains 32.7% of Earth's land.

December 1 is the 335th day of the year in the Gregorian calendar; 30 days remain until the end of the year.