estimated one million people demonstrated in New York City's Central Park against nuclear weapons and for an end to the cold war arms race as part of an ongoing campaign of anti-nuclear protests in the United States. It was the largest anti-nuclear protest and the largest political demonstration in American history. Over one million Venezuelans demonstrated on 1 September 2016 during the 2014–16 Venezuelan protests in Caracas, Venezuela, demanding a recall election against President Nicolás Maduro. The gathering was called the "largest demonstration in the history of Venezuela" with over 3% of the nation's entire population. An estimated crowd of 750 thousand to 1.5 million people gathered in Central Park in New York City on 22 April 1990 to celebrate Earth Day. An estimated crowd of over one million people gathered in Denver, Colorado, United States to celebrate The National Football Leagues Denver Broncos Super Bowl 50 parade. An estimated crowd of one million people gathered in London, United Kingdom on 23 March 2019 and marched to Parliament Square to show support for a second referendum on the UK leaving the European Union. An estimated crowd of 1.03 million people gathered in Hong Kong on 9 June 2019 and marched to Government Centre to protest against the Extradition Bill that, if passed, allows people to be extradited to China where basic human rights are not guaranteed. A two million people demonstration followed a week later and another one followed two months later (18 August). Methodology A method of determining how many people are at an event is the scientific analysis of photographs, video images, or both. Based on the quality of the image, it is possible to do a physical head count or to estimate attendance based on the density of people within similar areas. This permits the estimation of people over large areas or where parts of the image are obscured. An extensive discussion of how images were used to estimate the number of attendees at the Million Man March can be found at the Center for Remote Sensing at Boston University's website. References https://www.theguardian.com/world/2019/jan/15/kumbh-mela-hindus-converge-for-largest-ever-human-gathering-prayagraj-festival Gatherings