Behind the dusty stools and the old towels, under the broken telephones and the picture frames, amid the spider webs, sits one of the country’s most important collections of artifacts devoted to the history of African-Americans.

Painstakingly collected over a lifetime by Mayme Agnew Clayton — a retired university librarian who died in October at 83 and whose interest in African-American history consumed her for most of her adult life — the massive collection of books, films, documents and other precious pieces of America’s past has remained essentially hidden for decades, most of it piled from floor to ceiling in a ramshackle garage behind Ms. Clayton’s home in the West Adams district of Los Angeles.

Only now is her son Avery Clayton close to forming a museum and research institute that would bring her collection out of the garage and into public view. Just days before Ms. Clayton died, he rented a former courthouse in nearby Culver City for $1 a year to become the treasures’ home, leaving him to scrape together $565,000 to move the thousands of items and put them on display for the first year.