"In 2018 the course was officially certified, which means our marathon and half marathon can now be used as an official time for any events requiring a qualifying time."
Whanganui & Partners was a major sponsor of the event, Conder said, and their involvement had "helped the marathon grow".
"The support from Whanganui & Partners helped us increase our marketing and reach a bigger audience.
"We're expecting over a thousand competitors this year, with around 500 coming from out of town."
Whanganui & Partners' Jonathon Sykes said the 3 Bridges Marathon was "unique" and had potential to draw visitors to Whanganui, a major reason why the economic development agency supported events.
"The course is a unique location for a marathon, and it's great to have an event showcasing both the river as well as the strong sporting tradition in Whanganui," Sykes said.
"By attracting visitors, events provide an immediate boost to our economy through added spending on accommodation, hospitality and retail.
"There's also a longer term impact, with people who come here for an event often becoming repeat visitors or even residents."
The Pak'nSave Whanganui 3 Bridges Marathon will be held on December 12. Register at whanganuithreebridges.co.nz. Early bird prices are available until October 31.