Between 1916 and 2009 the strength of Queensland's unions waxed and waned. As was the case elsewhere in Australia, they benefited when compulsory arbitration was introduced and suffered when it was dismantled. But Queensland differed from the national norm in that for almost half a century after 1916 its workers were more likely to be unionists. This chapter argues that the extraordinary success of Queensland unionism, and its steady decline since the 1960s, must primarily be attributed to economic factors. The growth in rural employment after 1916 favoured union membership. When mechanisation subsequently decimated this workforce Queensland unionism lost its strength.