A donation of $116 million from the family foundation of longtime trustee Mitchell P. Rales will help share the museum’s collection in honor of the 250th birthday of the U.S. The National Gallery of Art will lend artworks to museums across the country. National Gallery of Art A new major gift to the National Gallery of Art will help the Washington, D.C., institution lend works from its collection to museums from Alaska to Kansas to Florida. The Mitchell P. Rales Family Foundation gave $116 million to the museum’s “ Across the Nation ” program, which celebrates the 250th birthday of the United States by sending art to and supporting exhibitions at smaller regional museums across the country. Mitchell P. Rales is a trustee of the National Gallery of Art. This gift marks the largest programming-related donation in the museum’s history.…