David Blair was born on November 20, 1787, in Donegore, Ireland, to Hugh Blair and Jane Thompson. His family immigrated to Philadelphia in 1802. Blair attended Jefferson College, and after receiving a license to preach, he travelled throughout the South as an itinerant minister. He settled in Indiana County, Pennsylvania, around 1816. As one writer later recalled, he was “one of the most profound theologians of his day,” and his “study of the Scriptures and church history made him a standard of authority on all subjects connected with the Christian religion.” He married Margaret Steel there around 1821, and they had at least five children: Samuel, born in 1821; Elizabeth, born around 1829; Margaret, born around 1832; John, born in 1832; and Sarah, born around 1836.
They lived in Indiana County, and Blair worked as a Presbyterian minister. In 1850, they owned $3,000 of real estate. A decade later, they owned $9,000 of real estate and $500 of personal property, and by 1870, his property value had soared to $20,000 of real estate and $5,000 of personal property. His wife Margaret died on April 6, 1865, and by 1870, Blair was living in his son John’s household. In 1880, he was living in his daughter Margaret’s household. He died in Indiana County on February 28, 1882.