He was there elected to the governing National Executive Committee of the YWL, moving to the headquarters city of Chicago after the convention at the NEC's request.
The NEC named Williamson its "National Industrial Organizer," attempting to build a mass movement of young communists among unionized workers.
During this interval of organizational poverty, Williamson worked at various day jobs to make ends meet, conducting his political activities at night.
His time there was short, as he returned in September 1924 to assume the role of head of the YWL, a job which he maintained until August 1928, when he was replaced by Sam Darcy for factional reasons.
He was released by the Young Communist League (successor to the YWL) for work in the adult party after the 5th National Convention of that organization, held in April 1929.
In 1949, John Williamson was convicted under the Smith Act in an attempt by the US Department of Justice to "decapitate" the leadership of the Communist Party USA.