He graduated from the City College of New York, and worked as a grocer while pursuing legal studies.
With the support of Tammany Hall, Sammon won the Democratic Party nomination for Manhattan's 11th New York State Assembly district in 1904, and defeated Republican candidate Joseph H. Simpson in 1904.
During his service on the 128th New York State Legislature, Sammon was appointed to the assembly committees on revision and charitable and religious societies.
[1] Sammon's 1920 candidacy for a seat on the New York Supreme Court was backed by the Farmer–Labor Party.
However, the New York City Board of Elections found that Sammon's petition for candidacy did not contain enough valid signatures, leading to his disqualification.