The number of women at the helm of America’s biggest companies pales in comparison to men, but is newly growing — and their tasks are huge.

What's going on: Jane Fraser took over at Citigroup this week, the first woman to ever lead a major U.S. bank. Rosalind Brewer will take the reins at Walgreens in the coming weeks (March 15) — a company that's been run by white men for more than a century.

Details: In Fraser's case, one task includes overcoming the perception of a "glass cliff," a heavily researched phenomenon of women being elevated as a company is in need of a cleanup.

What’s going on: Fraser, who’s been at Citi for nearly two decades, is stepping up as the bank faced an onslaught of trouble in recent years.

• (A few) things on Fraser's to-do list: quell regulatory concerns, up the bank's lagging stock price — and deal with fallout from the $900 million the bank accidentally sent to a group of creditors.
• On day one, Fraser promised the bank would get to net-zero greenhouse-gas emissions by 2050 — a climate goal promised by peers Bank of America and Morgan Stanley.

Brewer is taking over as Walgreens plays a big role in the country's largest undertaking: getting the masses vaccinated.

• Walgreens also faces existential threats: Insurers are pinching pharmacy profits. Brick-and-mortar pharmacies are also less essential in the Amazon era, when people can order what they need online.
• Competitor CVS bought insurer Aetna in 2018. Here's the sense on Wall Street: your move, Walgreens. (The company has used partnerships to infuse health services into its retail locations).

What to watch: 31 out of 500 of America's biggest companies are run by women, including Fraser and Brewer.

• It's both dismal and a feat, given it's close to an all-time record.

What's next: More churn for America's female leaders.

• Margaret Keane, chief executive at Symphony Financial, will step down in April. (Brian Doubles, a white man, will step in.)
• Thasunda Brown Duckett, a Black woman, will take over as CEO of money manager TIAA.