The depot opened on September 3, 1964, with buses originally operated by Chesterfield Corporation Transport. however they are now run by Stagecoach.
Seventy-seven vehicles leave the depot every day, travelling as far north as Barnsley and as far south as Belper.
Next year the firm will receive 57 brand new electric buses – a mixture of mini, midi and double deck buses.
It will be the biggest ever single investment in new buses in Chesterfield, leaving only 20-30 diesel buses in circulation.
Among the vintage vehicles on display to mark the anniversary are a 1959 Leyland PD2, owned by former driver and conductor Tony Stacey.
Tony drove the bus to Chesterfield twin town, Darmstadt, when it was gifted to Germany by Chesterfield Corporation Transport in 1989.
He also drove it back home to Derbyshire when new height regulations outlawed the vehicle in Germany some years later.
1. Sixty years of Stonegravels depot
Staff old and new and bus lovers mark the Chesterfield transport hub's anniversary Photo: Brian Eyre
2. Leyland PD2
Tony Stacey with his 1959 Leyland PD2 original Chesterfield bus Photo: Brian Eyre
3. A pair of Leyland classics
Natalie Shaw and Shayne Howarth, assistant operations manager at Stagecoach, with a Leyland tiger and a Leyland Leopard Photo: Brian Eyre
4. Old and new
Vintage vehicles alongside the newer Peak Sightseer, which links Chatsworth, Bakewell and Castleton Photo: Brian Eyre