As a young man, Green entered the house of N. L. & G. Griswold, merchants in the China trade on South Street in New York City, and displayed so much sagacity as a clerk that he was appointed supercargo of the ship Panama, a well-known tea clipper of the day, and of other vessels.

In 1833, he was admitted to the house of Russell & Co., in Canton (now Guangzhou), China, and there laid the foundation of his large fortune.

In 1839, on his return to New York, he married Sarah Helen, daughter of George Griswold, and carried on the China trade for many years thereafter, acquiring a fortune of about $7,000,000.

Always known as a man of clear views, strong convictions and great force of character, Green took an active interest in New York University, Princeton Theological Seminary and Princeton College.

He owned a town house on Washington Square Park in New York City and a large country house with much land at New Brighton on Staten Island where Curtis High School now stands.