He was the MNA for the riding of Papineau in the Outaouais region between 1989 and 2012, representing the Quebec Liberal Party.
In addition to being involved in the economic development of the Buckingham and La Lievre region, MacMillan was involved in the community as he is a member of the Knights of Columbus Buckingham Division since 1968 and the member of the Lions Club since 1973.
He also founded a Junior A hockey club, les Castors de Buckingham, in 1973.
MacMillan entered provincial politics as he was elected MNA for Papineau in a by-election in 1989[1] although he was a member of the Liberal Party since 1980.
On December 7, 2007, MacMillan was diagnosed with prostate cancer after multiple tests and received treatment during the first quarter of 2008.