The Carlsbad Marathon was once the San Diego Marathon and is rumored to be the second-oldest marathon on the West coast. The very first marathon ever held in San Diego, was run from Oceanside to Mission Bay. For many years the race was held annually in Mission Bay. In 1978 a new race was introduced in San Diego, The Heart of San Diego Marathon, which spanned the Coronado Bridge and finished at Qualcomm Stadium. In Motion, Inc. was hired to produce this new marathon in 1985 and three years later, negotiated a merger of San Diego's two marathons, the Heart of San Diego and the San Diego Track Club's Mission Bay Marathon. In 1990 In Motion took over ownership of the merged races and moved the race to Carlsbad where it remains today.
The San Diego Marathon name was officially retired just after the 2004 event, and the Carlsbad Marathon name was introduced. Carlsbad has been a gracious host to the Marathon and its participants, and has worked hand in hand with event organizers to create what many consider to be one of the finest marathons in the country.