Image copyright Getty Images Image caption Joan Johnson co-founded Johnson Products with her husband George

Joan Johnson, who has died aged 89, became the biggest supplier of Afro hair products in the United States.

Together with her husband she co-founded Johnson Products, one of America's most successful black-owned businesses, and the first to be listed on the American Stock Exchange.

The company developed many innovative products to help members of the black community look after their hair.

But the real root of the company's success was in the way it recognised the political power of hair and used its platform to champion what made African Americans different.

"I look at my mother as a pioneer," said Joan Johnson's son Eric in a statement after her death last week. "Because of her, people have been able to accomplish things they maybe didn't think they could."

Joan Betty Henderson was born in Chicago in 1929, though little is known about her upbringing.

At the age of 21 she married her high school sweetheart, George Johnson, a former salesman who worked as a chemist for a beauty products company.

It was the era of segregation, and beauty standards in America were set according to the physical attributes of white people. "The politics of respectability were the rule of the day," said Renée Richardson Gosline, a senior lecturer of management science at the Massachusetts Institute of Technology (MIT).

Many African Americans felt the pressure to straighten their naturally curly hair just to fit in among their white contemporaries. Thriving among their contemporaries was an even greater challenge.

Some straightening products were available, but not to the mainstream consumer, and George saw an opportunity. In 1954, with a $250 loan, he teamed up with a barbershop owner to create a hair straightener for black men.

Image copyright Getty Images Image caption Activists like Angela Davis used the afro hair style as a symbol of rebellion and black pride

The product, Ultra Wave Hair Culture, was trialled at the shop. With the barbershop so busy, George was left to look after both the manufacturing and the sales sides, and their partnership eventually splintered.

He and his wife later teamed up and together they went on to found Johnson Products. Success came almost immediately.

Joan Johnson worked behind the scenes as the company's treasurer, dealing with orders, accounts and logistics, and was an unsung hero in its success. During her first year, they more than quadrupled sales to $75,000.

As business continued to boom, the couple were forced to move warehouses several times to cope with the company's newfound growth.

There were many barriers along the way. One of their buildings - based in a predominantly white neighbourhood of Chicago - had its windows frequently smashed, and was once firebombed.

An electrical fire also burned down a production plant in 1964, destroying the company's inventory and killing an employee.

Image copyright NMAH, Smithsonian Image caption With Afro Sheen, Johnson Products tapped into a watershed moment in American political history

Despite setbacks, the couple achieved $1m in annual sales by 1961. They also released a new shampoo, a cream rinse, and Ultra Sheen - a women's hair straightening product that made the process cheaper and less time consuming.

But as the civil rights and Black Power movements gained strength throughout the 1960s, notions of beauty - not just politics - began to change, and many African Americans turned away from straighteners.

Instead, activists like Angela Davis sported natural afros, as a sign of rebellion against the white status quo and pride in African American identity. In response, Johnson Products launched Afro Sheen, a product to maintain afros, not change them.

The firm also tapped into this historical watershed moment through an advertising campaign championing the natural beauty of African Americans.

By the end of the 1960s, Johnson Products dominated the black hair-care market during the decade, and made $10m in annual sales.

The company's message "was much deeper than beauty", said Renée Richardson Gosline, the MIT lecturer.

"It was a statement about being proud of who you are as a black person, which was relatively revolutionary at the time."

As the company's national profile grew, so did interest from investors, and in 1971 Joan Johnson oversaw the company's public listing on the American Stock Exchange, the third largest exchange in the US.

The company also weathered an economic recession three years later, as well as a government order to print warnings on any products containing lye.

Their success attracted industry giants like Revlon into the market, as other companies realised the potential buying power of a community they had previously overlooked.

Competition grew, and so did segmentation within black hair styles as African Americans sought to express their individual identities.

Over time Johnson Products gained a reputation for lagging behind market trends, and in its waning years the company was riddled with family feuds.

In 1989, after eight straight years of losses, Johnson divorced her husband, took control of the company and was appointed as chairman.

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George stepped down as chief executive and was replaced by the Johnsons' son, Eric, who had been president until that time. But family loyalties clashed with business priorities - Eric ended up ousting his two brothers, reportedly because he was unhappy with their work.

Eric Johnson was widely credited with revitalising the company, but stepped down in 1992 after refusing to promote his younger sister to a more senior position.

Some family rifts did heal, and Johnson went on to marry George again after his second marriage ended in divorce. But as financial difficulties mounted, she oversaw the sale of the family business to pharmaceutical giant Ivax.

As a result of the $73m deal, Johnson Products passed from black ownership for the first time in its history. Some saw the acquisition as a sign of racial progress. For others, it marked a step back for the African American community, and the loss of a symbol so closely tied with black identity.

The legacy of Joan Johnson, and the company she helped build, is undeniable.

She and her family donated to several African American community groups, and Johnson served on the boards of organisations including Spelman College, a historically black women's college in Atlanta.

Johnson Products also helped propel black culture into the mainstream by sponsoring Soul Train, a music and dance show from Chicago that later became nationally syndicated for 35 years.

"[Johnson Products] wasn't some abstract thing to people in the African American community," said Katherine Phillips, a professor of management at Columbia Business School, in an interview with the BBC.

"It was an actual family who were working hard every day and serving the needs of the African American community when no-one else was doing that."