From The Development of the Movement by The Vegetarian Society UK:
Two followers of the Reverend Cowherd, the Reverend William Metcalfe and the Reverend James Clark, set sail for the United States with thirty-nine other members of the Bible Christian Church in 1817. Some of them remained vegetarian and provided a nucleus for the American vegetarian movement.

The current and increasingly publicized debate over the vegetarianism of Jesus Christ, brought to the mainstream largely by People for the Ethical Treatment of Animals, has a history in the United States. In 18th-century America various Christian sects practiced ascetism that included the "self-denial" of vegetarianism. However, it wasn't until the 19th century (as far as this historian has thus far been able to discern) that vegetarians took their contention about Jesus and vegetarianism public. It began in 1817, when Reverend William Metcalfe of England brought a small group of Bible-Christians, members of a church established a decade before by the Swedenborgian Reverend William Cowherd, to Pennsylvania.

Once settled in America, Metcalfe and his wife, Susanne, tried to teach their neighbors in Philadelphia about pacifism, temperance, abolitionism and vegetarianism--major tenets of their religion. His church did not enjoy widespread success, but what it lacked in size it gained in loyalty.

Metcalfe's little group of loyal vegetarians and their leader not only abstained from meat, they believed that Jesus had been a vegetarian. On account of teaching such a belief, Reverend Metcalfe, a congenial, pious and well-liked man, was unable to build a large congregation and sometimes suffered the slings of opposition to vegetarianism. Metcalfe's wisdom as a preacher and a person was attacked in the newspapers, and he was called "Infidel."

As a result, Metcalfe constantly had to struggle to keep the church financially stable. When he wasn't preaching, he was busy teaching in the church's tiny school, or writing and publishing two newspapers that reported on issues such as slavery, temperance and, it can be assumed, vegetarianism. Metcalfe's legacy of vegetarianism doesn't end at the church gate, for he was a force that brought together two other determined and courageous vegetarians. Those two individuals were Sylvester Graham and William Alcott, M.D. Together, Metcalfe and the two renowned vegetarian advocates formed the first national vegetarian organization in America.