Short answers, pulled from the story.
Philip Astley is credited as the father of the modern circus. Born in 1742 in Newcastle-under-Lyme, England, he set up the first modern amphitheatre for horse riding tricks in Lambeth, London, on the 4th of April 1768.
Philip Astley performed his stunts in a ring 42 ft in diameter, the standard used by circuses ever since. It was the minimum diameter that let an acrobatic rider stand upright on a cantering horse to perform tricks. Many performances are still held in a ring roughly 13 m across.
The word circus is borrowed from Latin circus, itself borrowed from the Ancient Greek kirkos. The early Christian writer Tertullian, in De spectaculis, claimed the first circus games were staged by the Greek goddess Circe in honor of her father Helios, the sun god.
The Englishman John Bill Ricketts brought the first modern circus to the United States. The first US circus building opened on the 3rd of April 1793 in Philadelphia, where Ricketts gave America's first complete circus performance, and George Washington attended later that season.
New circus, originally known as cirque nouveau, is a performing arts movement that began in the 1970s in Australia, Canada, France, the West Coast of the United States, and the United Kingdom. It combines circus skills with theatrical techniques and rarely uses animals, focusing on human artistry, story, and original music.
Cirque du Soleil, founded in Quebec in 1984, is the most conspicuous success in the new circus genre. Its estimated annual revenue exceeded US$810 million in 2009, and its shows had been seen by nearly 90 million spectators in over 200 cities on five continents.
The Circus Maximus stood in the valley between the Palatine and Aventine hills as the first circus in the city of Rome. Its final stone version could seat 250,000 people and measured 400m in length and 90m in width.