Phil Freelon, the renowned architect behind the Smithsonian’s National Museum of African American History and Culture, died Tuesday at the age of 66.

Freelon was diagnosed in 2016 with the degenerative neurological disease ALS, just six months before the museum opened.

Widely considered one of the nation’s most talented architects, Freelon designed numerous schools, museums and libraries—particularly in Washington.

“We in the field of museums, especially—we, and those colleagues of his in the field of architecture—have lost one of their leading lights and he will never be forgotten,” said Kinshasha Holman Conwill, deputy director of the National Museum of African American History and Culture. “He was generous, he was creative, he was kind. He was thoughtful, and he had a commitment to African American institutions and to architecture that was palpable and inspiring.”

Freelon, who served as lead architect, and David Adjaye, the lead designer, oversaw the years-long process to build the African American History and Culture from scratch. The three-tiered, bronze-coated structure has been widely lauded for its bold architectural statement.

“Illuminating this history, to have it memorialized here in a living way, not just about the history, but looking forward to the future is really something special,” Freelon tld DCist in 2016.

Richard Reyes-Gavilan, executive director of D.C. Public Library, said in a statement that Freelon also “played a critical role” in the library system’s transformation, designing both the iconic Tenley-Friendship and Anacostia neighborhood libraries. He was also an “early and authoritative voice” in the modernization of the Martin Luther King Jr. Memorial Library.

“His vision helped the District to see a bolder future for what libraries could offer,” Reyes-Gavilan added. “I and many others who have been impacted by his work will miss him dearly.”

Notably, Freelon was the mover and shaker behind both Atlanta’s National Center for Civil and Human Rights and San Francisco’s Museum of the African Diaspora. In 2011, he was appointed by former President Barack Obama to the U.S. Commission of Fine Arts.

Last year, Freelon and his wife, six-time Grammy nominated jazz vocalist Nnenna Freelon, founded the Northstar Church of the Arts in Durham, N.C.

“In lieu of flowers, Phil has asked that those who want to honor his legacy become sustaining donors of Northstar Church of the Arts, so that the same creative and spiritual energies that nurtured him throughout his life, may positively impact others, especially in his adopted home of Durham, North Carolina,” the Freelon family said in a Facebook post on Tuesday.

A memorial service is being planned for the fall.

This story originally appeared on WAMU.