Excerpts from Books and Wikipedia
"The Babi Dispensation began on May 22, 1844 in Shiraz, Iran. The Bab means "The Gate." He was the Prophet-Herald of Baha'u'llah. Mulla Husayn was the first to believe in the Bab. [Baha'I Glossary, p. 10, 36] "Two hours and eleven minutes after sunset Siyyid 'Ali-Muhammad makes His declaration to Mulla Husayn-i-Bushru'i." [Baha'I Chronology, p. 16] "The Báb was a merchant from Shiraz in Qajar Iran who in 1844, at the age of twenty-four, claimed to be a messenger of God. He took on the title of the Báb (...), meaning "Gate" or "Door", a reference associated with the promised Twelver Mahdi or al-Qá'im. He faced opposition from the Persian government, which eventually executed him and thousands of his followers, who were known as Bábís. . . . To Bahá'ís, the Báb fills a similar role as Elijah or John the Baptist; a predecessor or forerunner who paved the way for their own religion. Bahá'u'lláh, the founder of the Bahá'í Faith, was a follower of the Báb and claimed in 1863 to be the fulfillment of the Báb's prophecy, 13 years after the former's death." [Wikipedia]