Nicholas Van Slyck was born on July 28, 1829, in Pine Plains, New York. He graduated from Williams College around 1849, and he was admitted to the New York bar the following year. He married Elizabeth Manchester on November 1, 1854, and they had at least four children: Cyrus, born around 1856; Mary, born around 1858; Abby, born around 1861; and Emma, born around 1864. The family moved to Providence, Rhode Island, around 1855, and by 1860, he owned $2,000 of personal property.
In the spring of 1861, he received a commission as captain of Company B of the 1st Rhode Island Infantry. The regiment took part in the First Battle of Manassas, and Van Slyck mustered out on August 2, 1861. He then returned to Providence and resumed his work as a lawyer. He supported the Democratic Party, and he was nominated for state attorney general in 1864 and again in 1865. He supported Democratic candidate George B. McClellan in the election of 1864.
According to one writer, he eventually became “one of the most prominent lawyers in New England.” He became Providence’s city solicitor in 1874, and he also served as president of the local school committee. His wife died on December 23, 1890, and he died of pneumonia in Providence on March 3, 1892.