Matthias Bernard Hildreth was born in 1774 in Southampton, Long Island. His family moved to Johnstown in Western New York in 1797 and his father became a judge of the Court of Common Pleas in Montgomery County. Few details of Hildreth's life are available but he appears to have studied law and been admitted to the bar because he is listed in several local histories of Montgomery County as a member of the legal profession. The Military Minutes of the Council of Appointment of the State of New York indicate that he was appointed lieutenant of a company of grenadiers in the Montgomery County militia in 1797.
Matthias B. Hildreth was a presidential elector in 1804, Attorney General of New York State from 1808 to 1810, and from 1811 until his death in 1812, at the age of 38 years.