Mark Langdale with the George W. Bush Presidential Library Foundation says some donors prefer to remain anonymous -- so no names will be disclosed by the organization.
The foundation will oversee construction of the library, museum and public policy institute at Southern Methodist University campus.
The group had raised less than $3 million when the latest tax reports were filed in August.
The Dallas Morning News reports that's far short of its $300 million goal, but foundation officials expect the fund-raising will pick up after Bush leaves office Jan. 20.
Groundbreaking is expected in 2010.
Bush and his wife, Laura, have a ranch in the Crawford area. They're also buying a home in Dallas.