A major gift of top-tier contemporary artworks is headed to the Philadelphia Museum of Art from longtime museum supporters Keith L. and Katherine Sachs.

Amassed with the help of curators, the collection includes blue-chip post-1950 works by the likes of Ellsworth Kelly, Brice Marden, Jasper Johns, Donald Judd, Cy Twombly, and Gerhard Richter. Auction experts have estimated the collection of 97 works to be worth about $70 million.

Museum director Timothy Rub called the gift "one of the best contemporary art collections in the country." He says it ranks among the most important gifts the museum has received in its 138-year history.

The museum's modern and contemporary art galleries will be renamed the Keith L. and Katherine Sachs Galleries.

Additionally, 223,000 square feet of additional display space is in the plans with a Frank Gehry-designed renovation of the museum.

Keith Sachs, former CEO of Saxco International LLC, a principal distributor of packaging material, said, “Our collecting has been a process of both discovery and engagement, and one that has been richly rewarding and increasingly important in our lives. We believe deeply in the vision of those artists whose work we have collected in depth and in their enduring significance."