Fortune 500 list has counted 15 Black CEOs since first publishing in 1955

In March, Rosalind "Roz" Brewer will step in as Walgreens CEO, becoming the fourth Black Fortune 500 chief executive, and second-ever Black woman to permanently lead a Fortune 500 firm.

The big picture: In the history of the Fortune 500, there have been 1,800 different CEOs. Only 15 of them have been Black, reports Fortune's Phil Wahba. Another four have held interim positions.

"It's a stark reminder of how far corporate America's top decision-makers have to go during an unprecedented push by politicians, employees and even a stock exchange to diversify their top ranks," my colleague Courtenay Brown writes.

To mark the start of Black History Month, Wahba dove into the lives of those CEOs and examined why Black representation in corporate America has remained so abysmal for so long.

• One major problem is that too few Black professionals are put in management tracks. Representation of Black businesspeople is high in fields like accounting and marketing, but people who are successful in those parts of companies are less likely to become CEOs. It's typically employees who deal with profit and loss that rise to chief executive positions.
• Other systemic issues exist within recruitment practices. Companies routinely go to the same traditionally elite schools, such as the Ivy League, to seek out new talent. And the recruitment pool there skews white.
• Additionally, turnover rates tend to be higher for Black employees than for their white counterparts because they are less likely to feel valued or respected at work.

Go deeper: Wahba's profile of Fortune 500 Black CEOs is worth the read.