Which Twitter co-founder launched the mobile-payment company Square in 2009?

Jack Dorsey launched the mobile-payment company Square in 2009.

Dorsey co-founded Twitter and served as its first chief executive, but he also pursued a second major technology venture. Square, later renamed Block, began after Dorsey and Jim McKelvey looked for a simpler way for small businesses and individuals to accept card payments. The company developed a small card reader that connected to mobile devices, helping turn smartphones and tablets into point-of-sale tools.

Square was founded in 2009 and became one of the best-known financial-technology companies in the United States. Dorsey later returned to Twitter as chief executive in 2015 while continuing to lead Square. This dual leadership is a common source of trivia confusion: Dorsey was associated with both companies, but Twitter’s other co-founders, including Biz Stone, Evan Williams, and Noah Glass, did not launch Square with him.