Tradition holds that he was a younger son of a Scottish nobleman, took holy orders in middle age, came to America in 1708, and spent the remainder of his life in Albany and on the New York frontier.
Barclay's mission in America was three-fold. He was appointed chaplain at the Albany fort; was in the service of the Society for the Propagation of the Gospel in Foreign Parts (SPG) - the missionary arm of the Church of England; and also had instructions to start a church for English speaking people in the Albany area.
After several years of serving the Albany garrison, catechizing English, Irish, German, and even some New Netherland-ancestry Albany children, and while establishing a mission in the Mohawk country, Barclay's energy and initiative led to the founding of a permanent Anglican church in Albany. In 1714, the royal governor authorized Barclay and the church wardens to solicit subscriptions for the new church. Despite some local opposition, St. Peters Church opened in November 1716. Under Barclay's leadership, St. Peters emerged as an English-language cultural center in still Dutch-speaking Albany.
By that time, Thomas Barclay had settled in Albany. He married Anna Dorothea Drayer - a daughter of New Netherland and the mother of his four sons. Their family grew up in the rectory located on the "plain" north of the English church. The name of this now prominent figure was on a list of Albany freeholders in 1720.
Plagued by financial troubles throughout his time in Albany, Barclay began to suffer anxiety attacks which brought on depression. Anxiety became acute melancholy and eventually confined him to a darkened room. Despite increased compensation from the SPG, Barclay continued to decline and he died insane in 1726. The last dismal years provided a marked contrast to the energy and achievement that characterized his first decade in Albany.
The life of Thomas Barclay is CAP biography number 7210. Barclay's origins are still unknown to us. See the online presentation of R. Burnham Moffat, The Barclays of New York: Who They are and Who They are Not. Joseph Hooper's A History of Saint Peter's Church in the City of Albany (Albany, 1900), is the standard source for things related to the church - including the life of its first rector.