What is the value of a Blue Boy painting?

"The Blue Boy" painting was purchased in 1921 for $725,000. "The Blue Boy" has not been on auction since. Adjusting for inflation and assuming the painting has not appreciated in value, $725,000 equals an excess of 9 million dollars by 21st century standards.

"The Blue Boy" was painted by Thomas Gainsborough in 1770. The subject of the painting is believed to be Jonathan Buttall, the son of a wealthy merchant. Although the painting was created in the 18th century, the clothing worn by Buttall for the painting is from the 16th century. As of 2014, "The Blue Boy" is displayed at the Huntington Art Gallery in San Marino, Calif.