Two works by big league Impressionists dating from the early years of the movement are in the spotlight this spring.
Being offered for sale by the well-known dealers the Nahmads at Christie's New York rooms is Claude Monet's Le Pont du chemin de fer à Argenteuil.
With an unpublished estimate of around $35m (£18m), it will be a leading light in their May 6 sale of Impressionist and Modern Art. Christie's are predicting that it may break the auction record for Monet's work.
Monet painted Le Pont du chemin de fer à Argenteuil in the Northern Parisian suburb where he lived in the early 1870s.
Attractive riverside locations like this, with their pleasure boats and paths, were favourite recreational sites for Parisians and plein air Impressionist alike. But just as important to Monet from a pictorial viewpoint is the existence of the newly finished railway bridge with its steam train, a symbol of industrial progress that also provides a bold compositional element to this work.
The 23in x 3ft 2in (58.5 x 96.5cm) painting of 1873 is one of several versions of the scene painted by Monet, but with others in institutions it is the only one likely to come onto the market.
Also for followers of Impressionism, for the next three months both versions of one of Renoir's most famous images can be seen alongside each other.
A version of La Loge by Renoir that featured in Sotheby's Impressionist and Modern picture sale in London last month where it sold for £6.6m.
The 10 1/2 x 8 1/4in (27 x 21cm) oil on canvas is a smaller version of the work now in London's Courtauld Galleries that Renoir submitted to the first Impressionist exhibition of 1874 and was painted that same year.
Along with works by other Impressionists, this smaller canvas was submitted to an auction at Drouot in 1875 where it was purchased by Jean Dolfus. By 1941 it was in the United States in the Boston collection of Robert Treat Paine II.
The new owner of Sotheby's Renoir, Diane B Wilsey, who is president of the Board of Trustees of San Francisco's Fine Arts Museum, has agreed to lend it to the Courtauld's exhibition, Renoir at The Theatre, showing until May 25.
The show uses Renoir's iconic image as a focal point to examine the Impressionist's view of the theatre and modern Parisian life.
By Anne Crane