David Jackson McWilliams (1909-1986), dedicated 28 years of his life to La Casa del Libro. He maintained the museum operational after founder and first executive director Elmer Adler’s sudden demise. During his long and productive incumbency, McWilliams tripled the quantity of incunables in the collection, emphasizing in Spanish incunables. Under his directorship, many other important books were acquired, along with print works of local and international artists. McWilliams continued the labor of describing the books and nourishing the catalog of the museum, begun by Adler by way of manuscripts. While serving as La Casa del Libro’s executive director, he also worked as an English literature professor in the University of Puerto Rico, Rio Piedras Campus, and as an operetta singer. He became friends with many artists, like the marriage of Jack and Irene Delano, Antonio Martorell, Lorenzo Homar, and many other whom he received at the museum where he also resided.