It was Aretha Franklin who made Don Cornelius realise he had hit the big time. Just two years earlier, the impresario’s show Soul Train had been a Chicago thing, broadcasting local talent to local viewers. Now it was a national sensation and even the choosiest stars wanted to get on board. Franklin told him: “My kids love the show and I want to be a part of it.” Stevie Wonder improvised an ode to Soul Train. James Brown, convinced that somebody, probably a white somebody, must be behind such a slick operation, looked around its Los Angeles studio and kept asking Cornelius: “Brother, who’s backing you on this?” Each time Cornelius replied: “Well, James, it’s just me.”

He wasn’t bragging. As the host (or “conductor”) of Soul Train from 1970 to 1993, Cornelius was an avatar of cool, with his glorious afro, wide-lapelled suits and avuncular baritone, signing off each episode with a funky benediction: “I’m Don Cornelius, and as always in parting, we wish you love, peace ... and soul!” Billed as “the hippest trip in America”, Soul Train didn’t just beam the latest sounds from black America into millions of homes, but – with amateur dancers who became as integral to the show as the performers – the fashions, hairstyles and dance moves too.

“Most US music shows had been conservative when it came to race and representation,” says academic Jack Hamilton. “Soul Train was groundbreaking by having so many black people onscreen.”

The genesis of Soul Train is brought to life in the new US TV drama American Soul. “What I learned was there was Don Cornelius the host, and DC the man,” says Sinqua Walls, who plays Cornelius. “The only image we got of Don was the cool guy on Soul Train. On American Soul, we’re going to unpack the man who created all of that.”

Cornelius was born in 1936 in Bronzeville, Chicago. He cycled through various jobs – Marine, police officer, car salesman, DJ, newsreader – before becoming a reporter for local station WCIU in 1967, covering the civil rights beat. When Martin Luther King or Jesse Jackson came to town, Cornelius was there. He started thinking about making his own contribution to the movement: a music show that would portray African Americans at their best. At the time, black actors were largely confined to stereotypical supporting roles while black musicians were underrepresented on Dick Clark’s American Bandstand. So young black people saw themselves most often on the nightly news, and rarely in a flattering light.

“In the first episode of American Soul, Cornelius says, ‘I want black folks to be seen how black folks should be seen: strong, powerful and beautiful,’” says Walls. “Don had to butt heads with everybody: the buyers, the advertisers, people who wanted to invest in the show for ulterior motives. His challenges were daily.”

Taking the name from the live gigs he promoted in Chicago, Cornelius pitched Soul Train as “the American Bandstand of colour”. Debuting on WCIU on 17 August 1970 with performances by Jerry Butler, the Chi-Lites and the Emotions, it began as a low-budget affair, filmed in black and white. It was an instant hit with black viewers, Cornelius said, “not because it was a wonderful show but because it was theirs”.

To fulfil its potential, Soul Train needed national syndication, which required sponsorship. Snubbed by most brands, Cornelius secured the vital support of Johnson Products, the Chicago-based manufacturer of the black haircare range Afro Sheen. Cornelius also needed a big name for the first Los Angeles show on 2 October 1971, and beseeched Motown star Gladys Knight (played by Kelly Rowland in American Soul) to step up. Whenever she appeared thereafter, Cornelius would say: “If it weren’t for Gladys Knight, none of this would be here.”

One of that pivotal episode’s enraptured viewers was critic Greg Tate, then a high school student in Washington DC. “The fact that somebody could have an all-black audience dancing to all-black musicians every Saturday,” he says, “reflected a serious paradigm shift in American mass entertainment.”

The harbinger of a new era of black culture, Soul Train marked “a post-revolutionary moment when anything black people did on a certain scale felt political,” says Tate. “‘Black is beautiful’ and the Black Power movement had happened. Black culture was communicating blackness to black people and everybody else was just there to look over our shoulders while we had this love festival amongst ourselves.”

As host, Cornelius emanated a distinctly Chicago brand of cool: smooth, drily witty, somewhat strait-laced despite his flashy threads. Even his hair had gravitas. “Don had one of the best afros of his generation,” marvels Tate. “It was like having a Black Power salute coming out of your head!”

Feeling a civic responsibility to emphasise the positive, Cornelius ran a tight ship. The dancers were told: “Be on time, be tactful, be creative, be funky, be yourself.” Cursing, chewing gum and negativity were verboten. Unpaid and overworked (a month’s worth of episodes was filmed over a single weekend), dancers still queued in their thousands to audition, hoping to become mini-celebrities who taught the nation how to do the Robot, the Hustle and the Bus Stop. While inviting artists and activists to discuss political issues on the show, Cornelius practised what he preached by employing as many black directors and crew members as he could. He was like an adman whose product was blackness.

The 1970s were Cornelius’s Midas years. Soul Train’s new theme tune, composed by Philadelphia soul maestros Gamble and Huff, topped the Billboard Hot 100 under the title TSOP (The Sound of Philadelphia), and in 1977 Soul Train launched its own hit group, Shalamar, featuring two of the show’s star dancers Jody Watley and Jeffrey Daniel. Cornelius himself became a household name. “He was the guy who everybody knew in the community,” remembers his son Tony. “It used to bother me when people would call my father Don like they knew him.”

Spike Lee once described Soul Train as “an urban music time capsule”. As the 70s rolled on, it showcased the extraordinary fecundity of black music: giants such as Marvin Gaye, Tina Turner and Al Green; the eye-popping Afrofuturism of Labelle and the Undisputed Truth; the deluxe soul of Barry White, whose 40-piece orchestra wreaked havoc on the show’s balance sheet; the high glam of disco.

White artists were welcome, too, provided they were deemed to have soul. In 1975 Elton John, who personally requested to appear, was followed by a sketchy, skeletal David Bowie, who received an off-camera scolding from Cornelius for his sloppy lip-syncing. Cornelius had a good relationship with most artists – in a memorable 1977 episode he played basketball with Marvin Gaye, refereed by Smokey Robinson – but liked to maintain a professional distance. “He always talked about being careful about getting to know artists really well,” says Tony, “because when they need something and you can’t give it to them, you’ve lost a friend.”

Cornelius kept Soul Train relevant even when the latest sounds weren’t to his taste. In 1983, after a hiatus to recover from brain surgery, he gave the show a glossy relaunch for the era of MTV , broadening its remit to pretty much anything with a groove: Whitney Houston and Janet Jackson, of course, but also a-ha and Pet Shop Boys. The reboot hit a new ratings peak.

Hip-hop, however, was Cornelius’ great blindspot. In interviews with the likes of Kurtis Blow (“It doesn’t make sense to old guys like me”) and Public Enemy (“That was frightening!”) he couldn’t even pretend to relate to the new sound of black America. “Don was very much of his generation of ambitious, integration-oriented black executives,” says Tate. “They were middle aged and middle class and hip-hop represented everything they thought they were getting away from. They felt like these people were trying to drag them back down.”

As rap continued to rise, Cornelius knew his days as black America’s master of ceremonies were numbered. On 10 May 1993, he wished his viewers love, peace and soul one last time before ceding the spotlight to younger hosts, though he continued to steer Soul Train as producer. “Just like an athlete, he knew when it was time to go,” says Tony. “He told me that the days of a guy holding a microphone with a suit and tie on were over.” By the time Soul Train ended in 2006, after 35 seasons and more than 1,100 episodes, it was the longest-running nationally syndicated show in the history of American TV.

Cornelius’s final years were plagued by chronic ill-health, a bitter divorce and allegations of domestic violence. On 1 February 2012, he died from a self-inflicted gunshot wound. Jesse Jackson, Smokey Robinson and Stevie Wonder all spoke at his funeral but one friend told the New York Times that Cornelius was a difficult man to get to know: “You could fit all of Don’s friends in a phone booth and still have room.” Tony now runs the Don Cornelius Foundation, a non-profit dedicated to mental health and suicide prevention.

One of the tasks of American Soul is to illuminate the personality of an intense, private man who had private struggles behind his suave persona. Tate calls Cornelius “the Berry Gordy of television”: a businessman whose celebrity was a means to an end. “He wasn’t interested in himself being the brand; he was interested in owning the brand.”

I ask Tony whether his father would have enjoyed seeing DC, as well as Don Cornelius, portrayed on screen. “Probably not!” he says, laughing. “But it’s like medicine. You may not like the way it tastes but it’s good for you.”

• American Soul is on Thursday nights at 10pm on BET.