Haynes was born on July 18, 1753, in West Hartford, Connecticut, reportedly to a Caucasian mother of some status and an unknown man who was African or African-American.

[1] The most prevalent theory is that she was a servant named Lucy or Alice Fitch who worked for the John Haynes family of West Hartford.

[1] At the age of five months, Lemuel Haynes was given over to indentured servitude to Deacon David Rose, a blind farmer of Granville, Massachusetts.

[3] In fact, Haynes recalled at one point that Mrs. Rose “had peculiar attachment to me: she treated me as though I was her own child, I remember it was a saying among the neighbors that she loved Lemuel more than her own children.”[4] His indenture ended when he was twenty-one.

The Scripture, abolitionism, and republicanism affected his published writings, in which Haynes argued that slavery denied black people their natural rights to "Life, Liberty and the pursuit of happiness".

"[8] In this essay, Haynes advocated for the emancipation of enslaved peoples in America, condemning slavery as a sin and highlighting the irony of slaveowners pursuing liberty from Britain while depriving it to so many on American soil.

"Liberty Further Extended" was never published during Haynes's lifetime; it was discovered only in 1983, more than two centuries after he wrote it, by Ruth Bogin in a Harvard University archive.

In 1779, he went to live with the Reverend Daniel Farrand in Canaan, approximately twenty-five miles west of Granville in northwestern Connecticut.

[4] The following year, Haynes moved to the nearby town of Wintonbury, where the Reverend William Bradford instructed him in Greek and found him a local teaching job.

[4] In November 1780, Farrand and two other clergymen granted Haynes his license to preach, along with a position as temporary 'supply' to his home congregation in Middle Granville.

On March 28, 1788, Haynes left his pastorate at Torrington to accept a call at the West Parish Church of Rutland, Vermont (now West Rutland's United Church of Christ), where he led the mostly white congregation for 30 years –– a relationship between pastor and congregation rare in Haynes’s time for its length as well as its racial dynamic.

His contemporary white republican and abolitionist thinkers saw slavery as a liability to the new country, and argued for eventual slave expatriation to Africa.

In contrast, however, Haynes continued to passionately argue along Calvinist lines that God's providential plan would defeat slavery and lead to the harmonious integration of the races as equals.

He had composed his own epitaph, which was included on his gravestone as he had requested.Here lies the dust of a poor hell-deserving sinner who ventured into eternity trusting wholly on the merits of Christ for salvation.

In the full belief of the great doctrines he preached while on earth, he invites his children, and all who read this, to trust their eternal interest in the same foundation.While living in Middle Granville in the early 1780s, Haynes met and married Elizabeth Babbitt (1763-1836), a white schoolteacher.

She regularly listened to Haynes preach and, "looking to Heaven for guidance, she was led ... to make him the overture of her heart and hand as his companion for life."

Although Haynes was "highly honored" by Babbit's proposal, he hesitated to accept, doing so only after consulting a number of ministers and receiving their approval.

11 January 1803 Rutland, 3 March 1839 at sea)[4][14] Haynes was the first black abolitionist to reject slavery on purely theological grounds.

[17][18] Historian John Saillant (2003, p. 3) writes that Haynes's "faith and social views are better documented than those of any African American born before the luminaries of the mid-nineteenth century."