He then enlisted in the U.S. Army and was assigned to the Engineer Corps, but World War I ended before he was sent overseas.

[3] Gladstone set up a private law practice in Manhattan and was active in the Bronx County Democratic organization, serving as secretary of his district's county committee, as a delegate to judicial conventions, and on the law and speakers' committees.

[3] On April 2, 1935, Gladstone collapsed from a heart attack in the Assembly and rushed by ambulance to Albany Hospital.

However, on December 13, 1935, after leaving a meeting at the local Democratic club in the Bronx and returning home, he suddenly collapsed and died.

[3] Benjamin Gladstone Square, surrounded by Westchester Avenue, Hoe Avenue, and West Farms Road, a block away from Gladstone's residence at 1106 West Farms Road and previously called Fox Square, was named after him in 1937.