As soon as he turned 18 and became eligible for membership, Ben Gitlow joined the Socialist Party of America. Gitlow was a committed and active member of the party and he was elected a delegate to the New York state convention of the SPA in 1910, the year after his joining. In the fall of 1917, Gitlow was elected on the Socialist ticket to the New York State Assembly (Bronx Co., 3rd D.), and sat in the 141st New York State Legislature. He was one of 10 Socialists elected to the Assembly of 1918, all of them from New York City.