After the skyrocketing post-war and contemporary art auctions in early May, prices in the historic American art sales last week were seemingly modest, reports the New York Times. Several lots soared, a few soured, but overall a renewed market strength was evident for American paintings of the 19th and early 20th centuries. Yet many top-tier artists of yesteryear appear to be undervalued.

"These days, some artists of those eras are more affordable than even a decade ago," writes Souren Melikian, who also points out that "in American painting, fame remains the most important factor in the making of art prices," posing an opportunity for astute collectors to buy quality American art now.

Works by American art superstars such as Rockwell, Wyeth, and Hopper went for hefty sums, but fine works by noteworthy artists such as Alvan Fisher, Anthony Thieme, Wolf Kahn, Frederick Usher Devoll, among others, should have brought much more, according to Melikian.

Christie's reported its strongest American art sale since 2008. A $19 million Edward Hopper topped the $50 million sale. And Hopper's Kelly Jenness House wrangled $4.1 million, an auction record for a watercolor by the artist.

Sotheby's sale saw six Norman Rockwell paintings bring a cumulative total of $6.5 million, double the total presale estiamte. Charles M. Russell's tiny, 5 1/4-inch-high bronze An Enemy that Warns catapulted to $437,000 from a low estimate of $40,000.

A monumental painting titled “Early Snow in Yosemite Valley, Sentinel Rock” by Albert Bierstadt led Bonhams sale, bringing $338,500. The price reflected condition issues, according to Melikian, otherwise the work would fetch in the millions.