WILMINGTON, Delaware (AP) — From the streets of Harlem to the pitiful slums of Brazil, Gordon Parks focused his lens — and his life — on subjects that many people would prefer to ignore.

But the images that Parks captured as one of the most accomplished documentary photographers of the 20th century — and the first black staff photographer for Life magazine — are too powerful to shy away from. From the forgotten lives defined by violence and poverty to the unguarded moments of the rich and famous, he captured the human condition in a way that few others artists have.

"Bare Witness," an exhibit opened last weekend at the Delaware Art Museum, offers visitors a comprehensive and thought-provoking introduction to Parks' work. The museum is one of only five stops for the show, which debuted last year at the Cantor Arts Center at Stanford University and will be on display in Wilmington through January 4 before a final stop at Northwestern University's Block Museum of Art.

Born in Kansas, son of a farmer and the youngest of 15 children, Parks moved to Minnesota as a teenager to live with a sister after his mother died, dropping out of high school just short of graduation and struggling through a series of Depression-era jobs. He eventually landed work as a Pullman dining car waiter, a job in which he became fascinated with New Deal images of poverty captured by Farm Security Administration photographers in magazines left behind by train passengers.

His interaction with passengers, including Life photographer Bernard Hoffman and war photographer Robert Capa, only deepened his love of photography, and he eventually began his career as a freelance fashion photographer.

Parks moved his family to Chicago in 1940, and a photography exhibit the following year earned him a fellowship that allowed him to spend a year in Washington as an FSA photographer, a period in which he captured perhaps his most famous image, "American Gothic" (1942). An interpretation of the iconic 1930 painting by Grant Wood, Parks' photograph shows a black cleaning woman, Ella Watson, standing in front of an American flag while holding a mop and broom, echoing the stoic stance of the pitchfork-wielding farmer in Woods' painting.

"American Gothic" is one of 73 images that Parks, who died in 2006, helped select for the "Bare Witness" retrospective after being approached by The Capital Group Foundation, working in collaboration with the Cantor Arts Center.

Heather Campbell Coyle, associate curator at the Delaware Art Museum and a University of Delaware doctoral student in art history, was teaching a class in the history of photography when she learned of the Parks retrospective. She jumped at the chance to bring it to Wilmington.

"He's one of my favourite artists to teach," said Coyle, who used the opportunity afforded by the Parks exhibit to showcase 28 equally compelling documentary photographs from the DAM's permanent collection.

The Parks exhibit spans four decades of his work, including his first photo essay for Life, a 1948 examination of Harlem gangster Red Jackson. The danger that Parks faced is illustrated in the darkened shadows of "Night Rumble," in which a gang member, his back to the camera and arm raised, prepares to strike out at an unseen foe while two bystanders clutch each other in a fearful embrace.

"Just another one of the thousands of violences that explode in the ghetto every week," Parks wrote 20 years later in describing an emergency room visit prompted by a fight between a man and woman whose Harlem family he documented in a 1968 photo essay entitled "The Negro and the Cities: The Cry That Will Be Heard."

The dominant theme of the exhibit is not violence, however, but poverty, whether it be urban images reminiscent of the 19th-century New York City street scenes captured by Jacob Riis, or images from the rural South in the 1950s.

Parks' 1961 journey to the slums of Rio de Janeiro, where he documented the life of 12-year-old Flavio Da Silva and his family, provide some of the most haunting images in the exhibit, none more compelling than the portrait of a filthy, disheveled Flavio standing on one leg, the other crossed in front of him in a pose almost resembling a crucifix. The boy appears at once cocky and defiant, yet bewildered and desperate; his skeletal frame and sunken eyes conjuring images of a Nazi concentration camp survivor.

Another picture shows Flavio's brother Mario screaming in pain after being bitten by a dog, but one wonders if his agony stems more from the conditions in which he finds himself.

The power of Parks' work is enhanced by his use of deep shadows, offering a chiaroscurolike contrast that makes his subjects appear not just morose, but mysterious.

"They are so richly dark," Coyle noted.

While Parks' images sometimes sparked viewers to action, he was careful about crossing the line separating artist from advocate, exposition from outrage. Asked by Black Panther leader Eldridge Cleaver to join the militant group as its minister of information, Parks demurred, saying he would lose his objectivity. Revisiting the issue later, he opined that while he and Cleaver shared the black man's ordeal, they chose to act on it differently.

"I will continue to fight also, but on my terms," he said.

That's not to say that Parks found it easy to keep his distance from his subjects. In a narrative accompanying a 1963 photo essay about Malcolm X and the Black Muslim movement, Parks recalled how he sometimes drove through Harlem on his way home to the comfort of Westchester, New York, and how in his early days he missed the soft laugher of Harlem and "the security of black friends about me."

"Eventually, I found myself on a plateau of loneliness, not knowing really where I belonged," he wrote. "In one world, I was a social oddity. In the other, I was almost a stranger."

"Many times I wondered whether my achievement was worth the loneliness I experienced, but now I realise the price was small. This same experience has taught me that there is nothing ignoble about a black man climbing from the troubled darkness on a white man's ladder, providing he doesn't forsake the others who, subsequently, must escape that same darkness."