Short answers, pulled from the story.
Babylonian scribes carved a flat disk floating in an ocean called Bitter River onto the Imago Mundi artifact. This map surrounded the central landmass with distant regions labeled as foreign lands and mountains.
Cosmas Indicopleustes published Christian Topography in 547 claiming the Earth was a rectangle 400 days journey long. He dismissed spherical theory as pagan while describing four oceans surrounding a rectangular Earth enclosed by massive walls supporting the firmament.
Samuel Shenton set up the International Flat Earth Research Society known as Flat Earth Society in Dover England in 1956. This organization served as direct descendant of Universal Zetetic Society established by Lady Elizabeth Blount in 1893.
American writer Washington Irving maintained that Christopher Columbus faced church opposition to gain sponsorship for his voyage. John William Draper and Andrew Dickson White later used this narrative as element in their science versus religion conflict thesis.
A 2018 study reported by Scientific American found only 82 percent of 18 to 24 year old Americans agreed statement I have always believed world is round. Less than 2 percent acceptance exists across all age groups regarding firm belief in flat Earth.