Ferguson's 25 year anniversary was marked with the unveiling of the new stand.
Gill said: "To be at a club of our standing for so long is truly remarkable.
"In that time Alex has established himself as the most successful manager in British football history, winning countless trophies and creating numerous sides admired around the world for their flair and ability.
"Alex's contribution to United has been immense and the magnificent stadium we have here at Old Trafford is a testament to his ability and success.
"The board felt it right to take this unique step, as well as to commission Philip Jackson to create a statue to go alongside his other great pieces here of Sir Matt and the United Trinity (Best, Charlton and Law).
"These tributes are made with the grateful thanks of the owners, board, staff, players and fans of Manchester United, for the great pleasure Alex has brought us all over a quarter of a century."