By Cherri Gregg

PHILADELPHIA (CBS) –The Rosenbach Museum and Library used a chance blog-post inquiry to acquire a portrait once thought to be lost. The acquisition ends a 30 year mystery related to one of Philadelphia’s most prominent Jewish American families.

“We knew that this portrait by Thomas Sully existed somewhere,” says Museum Curator Judy Guston, who also says the portrait of Maria Gratz has been “lost” since the 1970s.

Maria was married to Benjamin Gratz, son of the patriarch Michael Gratz, who came to Philadelphia in 1759.

“He was a rather adventurous kind of guy who transported all sorts of things into Philadelphia during the time it was occupied by the British,” Guston explains.

Benjamin’s portrait sat on the wall of the museum, and last year, they decided to search for Maria by asking Susan Sklaroff write about it on her blog, “Rebecca Gratz & 19th Century America,” and urge her readers to check their attics and closets.

Three weeks later, Maria Gratz Roberts–the great-great-great granddaughter of Benjamin and Maria–called to donate the painting to the museum.

“I think she’s a romantic at heart, and I think in some ways we all are,” Guston says.

Several Gratz family portraits will be available at a free ceremony honoring the family on March 4th. For more info on the Gratz family portraits, go to www.rosenbach.org.