 He was arrested numerous times throughout the 1920s and 1930s for offenses ranging from burglary to murder.After serving a lengthy stretch in Sing Sing, McGrath ended up as an organizer for the International Longshoremen's Association on the Hell's Kitchen waterfront.With the notorious Joseph P. Ryan in control of the ILA, McGrath became the primary muscle on the waterfront, with gangsters like John "Cockeye" Dunn (who was McGrath's brother in law) and Andrew "Squint" Sheridan as his enforcers.