The very first Manjimup 15000 motocross event was held on 1 June 1980 at the Cosy Creek Circuit in Manjimup.

The spark for the Manjimup 15000 was ignited at the 1979 King of the Cross Motocross in Southern Cross, when the event went international as part of Western Australia’s 150-year celebrations. Witnessing the spectacle firsthand, Manjimup Motor Cycle Club members saw what was possible. If a small gold-mining town like Southern Cross could attract the world’s best riders, thousands of spectators, and global attention—why not Manjimup?

That vision became reality in 1980, when the inaugural Manjimup 15000 drew a crowd of 5,000 spectators. Throughout the decade, attendances swelled at the Cosy Creek circuit to as many as 10,000, cementing the event’s place on the international motocross calendar.

The name Manjimup 15000 was derived from the original value of the prize money, which at the time, was the richest motocross event ever held in Australia. Britain’s Roger Harvey was the inaugural winner.

Through the 1980s and into the new century, the Manjimup 15000 became a Foundation Day long-weekend tradition, drawing the world’s best riders and thousands of fans to Cosy Creek. The public holiday helped draw visitors to the event and region and support the locals who contributed to the event.

Under the early guidance of Trevor Holm, the Manjimup 15000 went from strength to strength over the next 30 years to establish itself as Australia’s most prestigious outdoor one-day motocross event.
Since the inaugural event in 1980 to today, the club has distributed more than $600,000 in prizemoney, peaking at a record $33,000 in 1988.

Apart from a few hiccups in the early years when the event was not run, the Manjimup 15000 was held annually on the WA Foundation Day June long weekend into the turn of the century – drawing International, National and State riders.
In fact, the Manjimup MCC has run events on this holiday weekend since the seventies when it hosted the very successful Australian Motocross Championships in 1974. Also, the 1980 Manjimup 15000 was not the first time international motocross riders competed at Cosy Creek.

Back in the early 1970s the Manjimup MCC hosted the second round of the International Motocross Series across Australia and New Zealand, with the first round traditionally held by the AJS Motorcycle Club at the Herne Hill Circuit on the outskirts of Perth.

Since then the club has played host to the Motocross of Nations (1992) and the World 125cc MX GP (1993).
In 2009 Dirt High Promotions took over the running of the event in partnership with the Manjimup Motorcycle Club as it was not run in 2006 and 2008 as the club was struggling for volunteer helpers.

Since then, the Manjimup 15000 has gone from strength to strength to again provide the largest one-day motocross event in Australia.