The message for the Discover our Land campaign, which started in January and is led by the county council, is now being spread at railway stations and on bus routes.
The adverts features supporters of the campaign that aims to promote the county as a great place to live, work, visit and invest.
Their locations include Morpeth Railway Station.
County council leader Peter Jackson said: “For too long, Northumberland hasn’t been fully recognised by the rest of the UK and beyond for its unique offer and special assets.
“Now, through Discover our Land, we are urging businesses and residents to work together and help spread the message about what is great about our county.”
Since the campaign launched, more than 200 businesses and individuals have signed up to support it and become ambassadors for the campaign.
Coun Cath Homer, the council’s cabinet member for culture, arts, leisure and tourism, said: “This advertising campaign will support the work we have already been doing to promote Discover our Land, as well as helping to engage with a wider audience.”
To find out more about the campaign, go to www.discoverourland.co.uk