SPOKANE, Wash. — Before Macklemore or Nirvana, this land was Woody Guthrie’s land.

It was 75 years ago that the celebrated folk singer traveled across Washington and Oregon, composing 26 songs that extolled the virtues of Grand Coulee Dam and the electricity it produced.

It was one of the most productive months of Guthrie’s career, and will be celebrated on Saturday with a gathering at the giant dam on the Columbia River that remains the nation’s greatest producer of hydropower.

The 26 songs composed in the spring of 1941 included favorites like “Roll on Columbia,” “Pastures of Plenty,” and “The Biggest Thing that Man has Ever Done.” Collectively they are known as “The Columbia River Songs.”

“He plucked tunes about the people, the mighty Columbia River, the beautiful Northwest landscape and the promise of prosperity from new hydroelectric dams,” said Libby Burke, an archivist for the Bonneville Power Administration, the Portlandbased federal agency that hired Guthrie. “We’re excited to celebrate the music of this great American songwriter and his 30-day employment with us back in 1941.”

The BPA planned to use the songs in a documentary about Columbia River hydropower, but the project was abandoned when World War II started. The film, “The Columbia,” was finally finished in 1949.

In honor of the anniversary, Washington Gov. Jay Inslee proclaimed Saturday as Woody Guthrie Day in the state.

Events at the mile-wide dam, located 80 miles west of Spokane, ran from 1 p.m. to 9 p.m. at the visitor center. There were panel discussions, readings and film screenings. There was no charge.

The BPA is a federal power marketer that sells wholesale electricity from 31 federal dams and one nuclear plant to 142 electric utilities.

Guthrie died in 1967 at the age of 55. He wrote hundreds of songs and influenced generations of musicians. His best known song is “This Land Is Your Land.” Many of his songs were about his experiences during the Great Depression, when he traveled with displaced farmers from Oklahoma to California and learned their traditional folk and blues songs.