The prime meridian (zero degrees), today is located in Greenwich, London, United Kingdom. Greenwich has not always been the agreed-upon prime meridian. In the 18th century most European countries chose a location unique to them and built their maps off of that reference point. It was not until 1884, when 22 countries met in Washington, D.C., United States, and voted the Greenwich meridian as the international standard.

Other key points of latitude are the Tropic of Cancer (23°27’ N), Tropic of Capricorn (23°27’ S), the Arctic Circle (66°30’ N), and the Antarctic Circle (66°30’ S). The Tropic of Cancer located in the Northern Hemisphere is the point on Earth that receives the most direct sunlight around June 21st as the North Pole tilts toward the sun. This latitude is mirrored by the Tropic of Capricorn in the Southern Hemisphere and receives the most direct sunlight around December 21st when the South Pole is tilted toward the sun. The Arctic Circle, which surrounds the North Pole, marks the point where the sun does not set around June 21st or rise around December 21st. Likewise, the Antarctic Circle, near the South Pole, is the location where the sun does not set around December 21st or rise around June 21st.