A COUPLE OF SUMMERS ago, my friend and I went to Olana, Frederick Church's Hudson Valley residence. Though Church had once been America's most well-known and highest-paid landscape painter, by the 1870s his artistic reputation was in decline, and he forsook painting to fling himself into creating a bizarre fantasy home. Olana is a sticky mix of faux Persian, Indian, Islamic, and medieval European styles. Though each of its parts might remind you of something real, together it makes an impossible, deliciously garish pastiche.

Church created, in both this Disney Castle-like home and in his paintings, pretty composites of things he remembered seeing; things you and I could recognize, like the peak of a certain mountain or the splash of a certain waterfall. He also created things he only imagined, but that you and I, because we had come to trust him, would think were real. He was, like the other painters of the Hudson River school, a Romantic propagandist: a 19th-century American who tried to keep believing, despite the Civil War, the Indian Wars, and the transcontinental railroad, that North America was a pure and pristine new Eden -- God's country.

The friend I went to Olana with is a nostalgic fellow, and I am a melancholic gal, so we are naturally suited to the wistful sighing and embarrassed giggling that Church's home and landscapes call for. He's an amazing painter, his work featuring deep, murky, purple-blue skies and psychedelic sunsets, with gold and pink light shooting down from heaven like the voice of the Lord. A lot of his paintings -- like those of late Hudson River school peers Albert Bierstadt and Thomas Moran -- are huge: several feet across, and so high that you have to stand way back from them and stretch your neck to see their tops. They make you feel, as much as anything else, like being out in the mountains: You feel small.

Frederick Church's work is nostalgic, melancholic. It's about knowing, though not wanting to admit, that the best is already behind us; that we have, by our very presence here in this amazing landscape, fucked it up.

This Tranquil Land, the glorious show now at the Frye, is a collection of Hudson River paintings. Neither Church nor many of the other big names from this school (Cole, Inness, Kensett, Whittredge) are included here. Many of the artists in the collection are considered "minor," and all of the canvasses are small. The size of these paintings is part of what makes this exhibit so wonderful. You have to get right up to them, and when you're looking at them that closely, nobody else can. It's a one-on-one thing. These pieces are less about awe and majesty than they are about humility. Many of these painters seemed to have had a sense of how we -- meaning the white folks who made and looked at and bought these paintings, who fetishized the idea of these places, who turned them into tourist destinations -- were making a mess of the American landscape.

A lot of these paintings are about beginnings of ends. There are paintings about the end of the day: Grand Maman at Sunset, A Sunset at Bristol, Marshes with Heron, Twilight. There are paintings about the end of the year: On a Winter Afternoon, November, Brook in the Catskills, Winter Twilight. These are works about periods of time almost at an end. Though painted after the Civil War, and at the start of a new phase of Western expansion -- when white Americans could have felt hopeful -- these paintings feel apprehensive, as if they know that they are looking toward the dark.

That sense of apprehension is very present in Jervis McEntee's 1863 Fire of Leaves. This twilight scene has a beautiful purple-gray sky. Night is coming on. The last spot of sun is sinking into the horizon. We're in the woods and there are two paths, but you can't tell where either of them lead. At the fork in the path, two children dressed in city clothes are hovering over a small fire. The fire is also the color of the leaves on the ground around them. Are they going to be warmed by the fire they've started? Are they going to burn the whole place down, and themselves too? Painted two years after the end of the Civil War, McEntee's canvas suggests that all is not yet well in the Union. These two kids are lost in the woods with dark coming on, and though there may be a path to lead them out, they don't know which it is.

My favorite painting in this exhibit is Lemuel Maynard Wiles' Twilight in the Catskills. You notice it from all the way across the gallery, because right in the middle of this brownish rectangle is an incandescent, radioactive-looking blob of creamy lime green. Green like a grasshopper cocktail gone bad -- an almost nauseating green. When you get up close enough to see the details, you see that the green is what would be, in a "normal" painting, a patch of clear blue sky. The rest of this sky, the part that in a normal painting would be white or gray clouds, is a dirty, mustardy color (what my brother calls "baby-shit yellow"), while the ground is a muddy brown-gray. The leaves on the trees look like they might remember having been red once, a long time ago.

Twilight in the Catskills, or anywhere near the Hudson River, was a favorite subject for American landscape painters. Who could resist that late afternoon light falling on brilliant red and orange and yellow fall leaves? But in this painting, Wiles suggests another kind of twilight, an end not only of a day, but of an era. By 1870, the Civil War had long been over and white settlers were being encouraged to invade more of the West. But something wasn't right. If ever the New World had been an Eden, we -- with our Yankee ingenuity, our love of commerce, travel, and machines -- were doing our best to annihilate this paradisiacal land.