John Jackson Walsh graduated from Boston University Law School and practiced law, serving as legal counsel for labor unions and holding a clerkship in Middlesex County. He transitioned into public service, supporting James J. Storrow in the Boston mayoral election and later being appointed to the city planning board. Walsh ran for various political offices, including the United States House of Representatives and Senate, although he was not successful in securing these positions. He held a leadership role in a state-wide historical council and faced professional discipline in 1934.

John Jackson Walsh's political career is marked by an intriguing blend of advocacy for labor unions and city planning with a notable legal scandal. His support for labor unions aligns with progressive economic policies, yet his role in city planning suggests a broader interest in urban development. Walsh's legal troubles, involving a breach of trust, add a layer of complexity to his public image, revealing a tension between his professional ethics and his political ambitions.