The library, which had been decentralized since 1920, was consolidated into a central facility under the direction of Department Librarian Ralph R. On May 23, 1962, the 100th anniversary of the library's establishment, Secretary of Agriculture Orville Freeman officially designated the library as the National Agricultural Library, making it the third national library in the United States.
In 1934, the collection reached 250,000 volumes in size, and the library began participating in the Bibliofilm Service, which, along with the American Documentation Institute and the Science Service, supplied microfilm copies of articles to scientists.
Many of the pictures in the Pomological Watercolor Collection are available online through the library's Digital Repository (see link below).
The NAL Digital Repository, created in April 2006, serves as a digital archive of historical USDA documents.
The subjects covered include horticulture, entomology, poultry sciences, and natural history.
Within the Special Collections, the Pomological Watercolor Collection holds over 7,500 original watercolors on botanical subjects created by USDA artists between 18, almost half of which are apples.