This is what I dug up online....
The Young Men's Progressive Civic Association (YMPCA) was formed on October 13, 1915. The YMPCA grew to membership of 750 in less than five months.
1916 saw a name change, with the YMPCA becoming the 'Junior Citizens', colloquially 'JCs' or 'Jaycees'. The St. Louis Junior Chamber of Commerce asked them to adopt the name 'Junior Chamber of Commerce', which was done.
Way too many chapters to pinpoint a specific locale, but by the look of the "10", I'd say 1920-1930.