AFTER 2003's "Greetings From Michigan: The Great Lakes State" earned critical raves for literate and kaleidoscopic chamber-pop that explored the history and character of his home state, Sufjan Stevens announced a bold plan: to record an album for each and every one of the United States.

Equal parts whim, impulse, creative challenge and marketing ploy, such a project probably seemed like a good idea at the time . . . assuming the then-28-year-old Stevens lived a good, long life and never took vacations except, possibly, to as-yet-unwritten-about states.

"I may regret that," Stevens admitted recently from his Brooklyn home, without any obvious regret, "but it was probably necessary for me to acknowledge and put into words my intentions and my propositions. I think sometimes it's better for us to do that, even if it's detrimental.

"It's still kind of a mysterious thing to me, and I have no idea what it means," he says of what has been dubbed the 50 States Project. "We kind of make plans and goals by suspending our imagination, not really knowing what's going to happen next. I don't think it devalues the goal of the project or the nature of it. It is what it is."

What it is now is two albums down, thanks to the July release of "Illinois," an ode to the Prairie State that ranks No. 1 at Metacritic.com, a Web site that calculates an album's critical stature based on a wide sampling of reviews from mainstream and alternative media. Last year's champion was Brian Wilson's "Smile," and with its lush and intricate arrangements, quirky instrumentation, gorgeous melodies and conceptual ambition, "Illinois" has provoked comparisons to Wilson's "Pet Sounds" and "Smile," as well as to Bob Dylan, Walt Whitman and, for the nu-hipsters, Iron & Wine and the Arcade Fire.

Though he hired a string section and choir, Stevens did most of the playing on the album, overdubbing about 20 instruments, including oboe (the one instrument he has seriously trained on), piano, guitar, banjo, saxophone, accordion, glockenspiel, recorder and such percussion tools as tambourine and sleigh bells.

Where "Michigan" reflected a lifetime of homegrown memories and impressions -- Stevens was born in Detroit and grew up there and in Alanson, a small lumber town in northern Michigan -- "Illinois" resulted from extensive research, four months' worth before the first song was written. Raw materials included Saul Bellow's novels, Carl Sandburg's poems, biographies of historical figures, scholarly studies of small towns and frontier life, accounts of industrial development and old newspapers, as well as stories and anecdotes from friends who have lived there.

The 22-track, 74-minute album is replete with place names (Chicago, Decatur, Peoria, Highland Falls), populated by folks as disparate as Abraham and Mary Todd Lincoln, Sandburg, Frank Lloyd Wright and serial killer John Wayne Gacy. There's even room for Superman in "The Man of Metropolis Steals Our Hearts," though his appearance on the album's cover created a small problem for Stevens's self-owned label, Asthmatic Kitty. Apparently, no one thought to get clearance from DC Comics to use a drawing of the famously trademarked figure, necessitating a cover change after the first run (and making that first run an instant collector's item).

Neither "Michigan" nor "Illinois" are likely to be included in chamber of commerce tote bags: They're not booster-style travelogues or "Come to . . . " seductions, instead reflecting what Stevens has called "the uneven textures of American life." One of "Illinois' " key tracks is the mini-symphony "Come On! Feel the Illinoise!," about the 1893 World's Columbian Exposition, which celebrated the 400th anniversary of Columbus's landing in America and valorized American technology and commerce. It becomes a bittersweet rumination on the effects of industrialism in which Stevens sings, "All great intentions / Get covered with the imitations /Oh god of progress / Have you degraded or forgot us?"

According to Stevens, "industrialism taught us that anything can be mechanized and that there's a value of efficiency and economy in packaging to reach the widest possible audience and get the greatest yield from that. So many elements in our culture have been conditioned by that standard, and music is no different. The music industry has sort of systemized song and art in a real mechanized way, and while it's sad that the industry is in decline because of the Internet and downloading, it's exciting because it's empowering songwriters with a particular vision and voice, creating a whole new level of interest for unique songwriting."

Stevens is talking about such peers as Conor Oberst (Bright Eyes), Sam Beam (Iron & Wine), Devendra Banhart, Joanna Newsom and Antony Hegarty (Antony and the Johnsons, whose debut album recently won Britain's Mercury Music Prize). They've been lumped into a movement, the avant-folk/acid-folk scene that Wire magazine last year dubbed "New Weird America." The one obvious commonality: They're from all over the map, geographically and musically.

Stevens -- his first name, Persian and pronounced "Soof-yahn," was bestowed by the leader of a spiritual sect his parents belonged to when he was born -- grew up on a classical path, studying oboe early and long, and teaching himself piano, on which he wrote what he calls "small concerti."

But, he adds, "I had always been listening to Casey Kasem's American Top 40 and loved the Beatles and the Rolling Stones, and I was looking at a lot of rock 'n' roll as well, even though I was playing classical music." He credits both with inscribing in him "a high value for melody."

Stevens did not pick up a guitar until he went to college, and it would dramatically change his path. He calls the piano "somewhat of an overwhelming instrument" and says his compositions on it were "somewhat pretentious, Readers Digest-versions of classical melodies incorporating all the flourishes of a romantic piano concerto with my understanding of pop music. . . . The guitar, because it's so personal and intimate and portable, lends itself to accompanying the human voice, and I think for me, the real revelation happened in discovering my own singing voice."

That was after attending Hope College in Holland, Mich., where Stevens was in various local bands, notably the folk rock group Marzuki, in which he played whistles, and garage band Con Los Dudes. (He has joked, "I was promiscuous with style.") Neither afforded him a showcase for a voice that is even now soft and tender, what one writer described as "a confident whisper."

He was, Stevens says, "self-conscious about my singing because I wasn't very good: I had a hard time with pitch, a hard time staying in tune, even moving up and down the scale -- my range was very narrow. The piano, because of the sonic quality of it, wasn't allowing me to experiment and discover the character value of my voice. It was necessary for me to move away from piano, from classical music and my sort of pretensions about it, and move on to something more primitive, like folk music."

Five years ago, in his last semester at Hope, Stevens made his first solo album, "A Sun Came," playing 18 instruments and revealing an assured-yet-experimental pop sensibility. He formed Asthmatic Kitty with his stepfather and followed up a year later with the instrumental "Enjoy Your Rabbit," inspired by the Chinese zodiac.

Nonetheless, Stevens pretty much abandoned music after moving to New York to study in the master's program for writers at the New School for Social Research. "When I went to graduate school, I wasn't interested at all in being a musician or performing."

At the New School, Stevens was particularly drawn to the short story.

"For me, it was the perfect form in that it required an economy of ideas and of words, and a certain kind of editing and censoring and rendering. I always admired the brevity of an entire narrative in a few pages. That's what I was working at, and, ultimately, that would lead to a novel -- but it never happened."

Where it did lead Stevens, ironically, was back to music. A lot of his work in the writing program involved stories about Michigan families and Michigan people. "When I went back to songwriting, I was still preoccupied with the subject of Michigan, and I couldn't do away with it," Stevens admits. "It was kind of like a process of psychotherapy, bringing into realization these stories of place and geography and memory. It was definitely accidental, a slow discovery."

As he put together songs for "Michigan," Stevens saw it as "kind of an isolated project meant to stand on its own; I never intended on playing live. But I had so many solicitations and invitations to play [after 'Michigan's' release] that I just started doing that more, and [touring] sort of came after."

Still, Stevens didn't quit his job in the children's book division of Time Warner until last spring, when he toured not "Michigan" but "Seven Swans," a banjo-dominated album full of austerely beautiful meditations on love and Christian faith. And he'd begun work on "Illinois," saying: "It was somewhat of an exercise in taking myself seriously and keeping to my word and wondering if I could do it, wondering if I could succeed in constructing an album based on research and observation and theory, with the kind of emotional distance that I didn't have with 'Michigan.' "

Writing about Illinois -- a state Stevens had rarely thought about, much less visited, despite its proximity -- brought out the researcher in him. What interested him, he explains, is "the nervous system of a geography and a particular place and those things that are concealed below propaganda and below advertisement. Sometimes it's a difficult task to get entrenched in that and what it really means because there is such an obstacle of propaganda."

"What I discovered was sort of a strange emotional reaction to the subject, an infatuation with Mary Todd or with serial killers, or a real critical position on [certain things] I wasn't expecting. My infatuation with this record seems to be a lot on industrialism, for some reason. I don't know why, and I don't even know if that communicates, but that definitely was a kind of undercurrent to everything that I was writing about."

You can spot Stevens's literary instincts not only in his wisely observed and trenchantly detailed lyrics but in the poetic titles attached to songs, or even in such instrumental interludes as "A Short Reprise for Mary Todd, Who Went Insane, but for Very Good Reasons."

"Maybe it's because a lot of what I was reading about was from the turn of the century, and the media and newspapers that I was using as resources were informing the syntax in my language," Stevens suggests. "Back then there was still this sort of Victorian obsession with high-mindedness and eloquence and rhetoric, and it took pages and pages to say the simplest thing. Now there's an economy of language, and we don't have the time or the resources for that."

As he tours, Stevens is getting "what about us?" questions regarding the 50 States Project -- the next ones have been rumored to be Oregon and Rhode Island, though the latter may be the result of a joke he made about Rhode Island being just a 7-inch single "because it's the smallest state." There's talk of farming states out to other artists and perhaps taking on a producer's role -- sort of a "Sufjan Stevens Presents . . . " -- but he may just go ahead with what he's called "a ridiculous proposition."

"Sometimes I'll just say something to appease the writer, which isn't fair at all," Stevens admits. "Part of it is because I'm just not sure what I'm going to do, and I don't want to commit to anything. I have a lot of other things I want to work on, and I might want to start writing fiction again."

SUFJAN STEVENS -- Appearing Tuesday at the 9:30 club.

The 50 States Project: Sufjan Stevens aims to record a CD for each state. His latest is "Illinois."