The pockets of America where Walmart is king

The cities and towns where Walmart gobbles up more than half of all grocery sales are concentrated in the South and the middle of the country, illustrating a broader division in U.S. retail.

Why it matters: Retail has become one of the forces driving American inequality. While some cities build glitzy, revamped main streets and get same-day shipping, others have few options beyond Walmart super-centers and dollar stores.

By the numbers:

• Walmart owns 50% or more of grocery sales in 203 U.S. markets, per an analysis by the Institute for Local Self-Reliance, a nonprofit research and advocacy group that opposes concentrated economic power.
• In 38 of those markets, Walmart has 70% or more of the grocery sales.
• And in some places, the retail giant has virtually wiped out all other competition. Walmart owns 95% of the market in Portales, New Mexico; 95% in Atchison, Kansas; and 90% in Guymon, Oklahoma.

The bottom line: No grocer in U.S. history has ever been so dominant.

Yes, but: As politicians and consumers alike raise concerns about the outsized economic power of big companies, Walmart keeps growing — largely under the radar.

"The political pressure just isn't there to investigate Walmart," says Sally Hubbard, a director at the Open Markets Institute and a former assistant attorney general in New York's antitrust bureau. "The places where Walmart has large grocery market share are not places where policy activists live."

Go deeper: Two Americas, divided by how we shop