[2] Rumsey arrived in Chicago on July 28, 1835, to work at Newberry & Dole, a shipping company owned by his uncles.

However, soon after they became partners the company began to focus on purchasing grain, operating out of a small warehouse on the North Side of the city.

In September 1939, the firm sent the first-ever shipment of grain made in Chicago (2,900 bushels cosigned to Black Rock, New York).

Later, Henry Towner joined as a partner and the firm was renamed Rumsey Brothers & Co, a name it would hold for decades thereafter.

At the time of Rumsey's death, the only living charter member who had similarly maintained uninterrupted membership was Marcus C. Stearns.

As president, he implemented bold changes, which included obtaining a new charter for the board as well as putting in place a modernized system of grain inspection and grading.

"[citation needed] His efforts to implement strict inspection standards helped to give Chicago a strong reputation among American grain markets.

At the mass meeting in Metropolitan Hall a few days after the Battle of Fort Sumter, Rumsey delivered a stirring address.