PORTLAND — The Salt Institute for Documentary Studies announced Wednesday it has purchased a building in Portland’s Old Port district as a first step toward a major expansion of its college-level programs.

Founded in 1973 as an innovative high school English program in Kennebunk, Salt has evolved into a credit-granting undergraduate and graduate program affiliated with the University of New England and the University of Maine at Farmington.

It is perhaps best known as the publisher of Salt magazine, a quarterly that features photographs and documentary writing about Maine life.

It often has been likened to Foxfire, which documented crafts and folklore in the South.

“We sort of invented the wheel at the same time,” said Salt founder Pam Wood. “We began in Maine at the same time Foxfire was beginning in Appalachia and we didn’t know about each other.”

In its announcement, Salt said it plans to renovate the Exchange Street building to provide a facility for classrooms, photographic darkrooms, library, gallery and archive for the Salt Collection of Maine Life, a photographic and audio record of contemporary Maine life, folklore, crafts and memories.

Building renovations are estimated at $400,000, half of which will come from loans of $100,000 each from the city of Portland and the Coastal Enterprise Institute of Wiscasset.

Proceeds from the sale of the buildings in Portland’s West End where Salt has been based since 1989 went toward the $520,000 purchase of its new location, Wood said.