Football, American, distinct type of football that developed in the United States in the 19th century from soccer (association football) and rugby football. Played by professionals and amateurs (generally male college or high school teams), football is one of the most popular American sports, attracting thousands of participants and millions of spectators annually. The forerunner of American football may have been a game played by the ancient Greeks, called harpaston. In this game there was no limit to the number of players. The object was to move a ball across a goal line by kicking, throwing, or running with it. Classical literature contains detailed accounts of the game, including its rougher elements, such as ferocious tackling. Most modern versions of football, however, originated in England, where a form of the game was known in the 12th century. In subsequent centuries football became so popular that various English monarchs, including Edward II and Henry VI, forbade the game because it took interest away from the military sport of archery. By the middle of the 19th century football had split into two distinct entities. Still popular today, these two sports included the football association game, or soccer, and rugby, in which players ran with the ball and tackled. Modern football evolved out of these two sports. The football playing field is rectangular in shape, measuring 100 yd (91.4 m) long and 53.5 yd (48.9 m) wide. At both ends of the 100-yard dimension, white lines called goal lines mark off the entrances to the end zones. Each team defends one end zone. A team must carry, pass, or kick the ball into the 10-yd (9-m) end zone on the opponents' half of the field to score. Lines parallel to the end zones cross the field at 5-yd (4.5-m) intervals. These lines give the field a resemblance to a large gridiron. Another set of lines, known as the sidelines, runs along both sides of the field. In addition, two rows of lines, called