(CNN) Phil Freelon, who is best known as the architect of the Smithsonian's African-American history museum in Washington, has died. He was 66.

Freelon died Tuesday, daughter-in-law Kate Sheppard said. He had been diagnosed with the neurodegenerative disease amyotrophic lateral sclerosis, or ALS, in 2016.

In addition to designing the National Museum of African American History and Culture, Freelon was the mastermind behind Atlanta's National Center for Civil and Human Rights and San Francisco's Museum of the African Diaspora.

Former President Barack Obama appointed him to the US Commission of Fine Arts in 2011.

Freelon and his wife, Nnenna, founded the Northstar Church of the Arts in Durham, North Carolina, in 2018. The family posted on its website that it is planning a memorial service in the fall.

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