A STROLL through the landscapes of George Inness at the National Gallery takes you out in the country, into fields a heightened green from the rain, among blushing maples and rusting oaks.

You don't see his landscapes, you feel them -- the oppressiveness of a muggy day when the sky hangs low, or the relief when storm clouds scud away in succession, leaving the air clear and smelling like damp hay.

Painting in America in the second half of the 1800s, Inness chose not to take the popular path of the Hudson River School. Its dean, Frederic Edwin Church, had painted monumental landscapes -- travelscapes of volcanoes and falls to stir the untraveled masses. But Inness inspired involvement, not awe. He preferred the everyday pastoral scene, often generalized to no one place in particular. Looking to European painters for cues, he pursued the pale hues and broad brushstrokes of the French Barbizon school while depicting the Catskills and the Delaware Valley.

While his contemporaries were painting every leaf to achieve an accurate representation of nature, Inness was producing "more of a painting than a picture," noted a critic in 1894. He was not at all averse to blurring details. And while other painters revered idyllic landscapes, preferably without people, Inness nearly always included some sign of man -- farm animals, a barn, even a steam train. He called it "the civilized landscape." Often a speck of a man was included to give scale -- and to draw the viewer into the painting.

So modern was Inness that his landscapes have been compared to Mark Rothko's minimalist rectangles of color. Stand back and squint at Inness' landscapes, and his colors do have a way of layering themselves. In a rural Italian landscape, "The Monk" makes his thoughtful way under a canopy of olive trees lining up horizontally across an already striated sky.

Inness always understood that a painting could have beauty and form apart from its subject. Late in his life -- in the 1890s, when the times caught up with him and acclaimed him America's greatest landscape artist -- Inness painted even more abstractly. Cows became ephemeral ghosts, rocks were loosely painted, and a tree trunk became a reservoir of light.

GEORGE INNESS -- In the National Gallery of Art's West Building, through September 7.