The collection of more than 30,000 items, some dating back to 1850, have been donated by professional and amateur photographers.
The project, called Cornish Memory, received Â£225,000 from the Heritage Lottery Fund which was used to create the website and digitise the media.
Organisers plan to add thousands more images over the coming months.
Manager Claire White said the project "relied heavily" on volunteers and the idea came from the fact that numerous collections were not accessible to the public.
She said: "We wanted to bring the various collections together to make it available.
"We started work on the project in 2012 and still have thousands to add."
Ms White said she was in conversation with the Heritage Lottery Fund for further grants and was searching for alternative funding to help pay for the project in the future.
A photo, film and audio archive documenting Cornish life has been made available online.