[1] Born and raised on the South Side of Chicago, in a family with Irish heritage, Sammon began learning to play the piano as a young child.

He learned traditional Irish folk songs by ear while listening to records with his father, Martin Sammon Sr., a Chicago police officer.

After five years with Otis Rush, in which he played on Rush's 2003 DVD, Live Part One, and on Martin Scorsese Presents the Blues: A Musical Journey (which won Grammy Awards for Best Historical Album and Best Album Notes) - Godfathers and Sons,[7] Sammon was contacted by Phil Guy: "It was late night and I was home when the phone rang.

[9][10] In September 2015, Sammon made an uncredited appearance on the television program Bizarre Foods with Andrew Zimmern, in the episode "Delicious Destinations—Milwaukee".

Sammon's influences included Peter Sliwka, Dr. John, Scott Joplin, Professor Longhair, Keith Jarrett, Chick Corea, Otis Spann, Pinetop Perkins, Ray Charles, Eubie Blake, Fats Waller, Stevie Wonder, Donny Hathaway, Curtis Mayfield, and Bruce Hornsby.