The Boston Athenaeum has announced major expansion plans that will add nearly 20,000 sq. ft. to the historic independent library. The long-term lease for a space adjacent to the existing Beacon Street location will add room for growing collections, events, and the library’s existing catalogue of more than half a million books.

“Contiguous space has become available only a handful of times in the last century,” said John S. Reed, president of the library’s board of trustees. “We appreciate the singular opportunity to enter into a long-term lease.” Reed said the project will take approximately two years to complete.

The library first opened in 1807 and moved to its current location on Beacon Hill 42 years later. Its members have been some of the most distinguished writers in American history including Ralph Waldo Emerson, Louisa May Alcott, Francis Parkman, and Amy Lowell. Rare books and collections line the library’s shelves, including 17th century documents from Boston, portions of George Washington’s personal library, rare works on Native American languages, and a large collection of contemporary artists’ books.

While there have been occasional renovations over the last 170 years, the library has been in need of additional space, not only for members but also for employees. “We will be able to move employees out of improvised workspaces that developed over time in the architecturally-significant rooms at [the current location], and into connected, efficiently-organized offices [in the new location],” said Creelea Pangaro, the vice president of the library’s board.

In addition, the library will be adding to its salon-like spaces in which members have gathered for generations.

The expansion plans follow the announcement last week that library director Elizabeth Barker intends to step down at the end of March. According to The Boston Globe, Barker’s four year tenure was marked by disputes with staff and the resignation of numerous employees.

Pangaro said the expansion is a proud moment for the institution. “[It] will build on the library’s legacy and demonstrate our investment in its continuation and betterment, far into the future.”