Hardenbergh was a wagonmaker in Ulsterville, a hamlet of Shawangunk, and gave up his business when a law creating a tax on manufacturers caused him to believe it was unjust.
He was opposed to the levy of the tax for the payment of the railroad bonds, something that got him re-elected multiple times.
However, his election to the Assembly allowed him to establish his own bill within the legislature, resulting in a passing of a law that the state would take over the land, without taxing the county for the sales, and cancelled all previous sales of land from the county to the state.
[5] Hardenbergh died on January 10, 1893, and was buried in the New Prospect Dutch Reformed Church Cemetery in Pine Bush, New York.
His paternal grandmother, Maritje Hasbrouck Hardenbergh (a 2nd cousin of her own husband), re-married to Abraham Jansen (1782-1847), whose sister was Cornelius's mother Rachel.
His paternal great-grandfather, Jacob Rutsen Hardenbergh, was a co-founder of Queen's College in 1766, now known as Rutgers University.
He was a descendant of Louis DuBois, a Huguenot who fled religious persecution in France and helped form New Paltz, New York, as well as the Hasbrouck family.
In 1885, he served alongside his fourth cousin, once removed, Gilbert D. B. Hasbrouck, who was the Ulster County representative from the 2nd District.