Matthew Smith Austin was born in June 1830 in New York to Russell Austin and Martha Smith. His mother died around 1833. His family probably moved to New Jersey sometime before 1841.
He and his father were living in Neosho Falls in the Kansas Territory in 1860, and he was working as a printer. He returned to the East Coast soon afterward. He enlisted in the Union army on August 24, 1861, and mustered in as a private in Company I of the 5th New Jersey Infantry later that day. He became a commissary sergeant soon afterward, and he was eventually promoted to 2nd lieutenant. In January 1863, he hoped "to see an order for 300,000 men to fill up the old regiments. Draft them, if they would not enlist promptly...I should like further, if it were possible, (and it is) to see the ten or more thousand Deserters compelled to serve their three years from the time of their apprehension." He added that the "President and Congress [ought] to convince the north that it means to win, even if it have to call into the field every man able to bear arms." He mustered on September 7, 1864.
Austin lived in Trenton, New Jersey, after the war and worked as a printer. He married Sarah Jane Bell there on December 26, 1872, and they had five children: Edith, born in May 1875; Henry, born around 1877; Charles, born around 1879; Susannah, born in November 1881; and Harriet, born in March 1886. He remained in Trenton for the rest of his life, and he died there on January 13, 1904.