Short answers, pulled from the story.
The Edict of Torda was signed in the year 1568. This decree granted legal recognition to four religions and marked the first time a government officially acknowledged that God was a single being and Jesus Christ was not equal to God.
The Unitarian Church of Transylvania was founded by the preacher Ferenc Dávid. Dávid was a former Calvinist bishop who preached a message of radical tolerance and rational inquiry in the Principality of Transylvania.
The name Unitarian first appeared in print in the year 1600. The word was used again in 1673 by Henry Hedworth and gained popularity through the works of Stephen Nye.
The first avowedly Unitarian congregation in England was opened in 1774 by Theophilus Lindsey. This church was located at Essex Street in London and remains the headquarters of British Unitarianism today.
King's Chapel in Boston officially accepted the Unitarian faith in 1782. The church settled James Freeman as its rector and revised the Prayer Book into a mild Unitarian liturgy.
The American Unitarian Association began to allow non-Christian and non-theistic members in the 1890s. This decision led to the formation of Unitarian Universalism and the eventual creation of the American Unitarian Conference in 2000.