Former President Trump became the first Republican presidential nominee in more than three decades to earn more than 1.1 million votes in Los Angeles County last year, when his campaign attracted more than 375,000 new voters in what is otherwise a solidly Democratic fortress.

But Trump’s success in finding new votes in the nation’s largest county was overshadowed by an even more opportunistic campaign — Joe Biden’s. The 46th president gained 500,000 more votes in Los Angeles County than the previous Democratic nominee, former Secretary of State Hillary Clinton, had in 2016.

That pattern repeated itself in counties large and small last year, as both Biden and Trump drove turnout to a zenith not seen since before American women got the right to vote in 1920. Trump made substantial gains, improving on his 2016 performance to become the most-voted-for Republican presidential candidate in history — but lagging Biden, who earned more votes than any candidate to ever run for president regardless of party.

More crucially, as both parties start plotting their next midterm and presidential election strategies, the divide between the most heavily populated and the least populated counties in America continues to grow: The Hill's analysis of new data from the Census Bureau shows Biden won 91 of America’s 100 largest counties, while Trump carried 95 of the 100 counties with the smallest populations.

The Census Bureau data shows a widening gap between urban America, where populations are booming and economic activity makes up an increasing share of the nation’s gross domestic product, and rural areas, where people are moving out or dying and where communities are struggling to make a comeback.

Trump won 65 of the 100 counties that lost the greatest share of their population. All 35 of those shrinking counties that Biden won are heavily African American rural areas in the Deep South or Texas.

“We’re becoming more diverse, we’re becoming more urban, and most of that is happening outside of places Trump won,” said William Frey, a senior demographer at the Brookings Institution. “Even though Trump did better than he did in 2016 in some of those bigger places, the groups he was getting are shrinking parts of those populations.”

Across the nation, Trump improved on his vote share in all but 43 of the 3,113 counties that make up the United States — not including Alaska, which does not have a traditional county government structure. Biden improved on Clinton’s vote totals in all but 272 counties.

Many of those counties where Biden outperformed Clinton by huge margins made the difference in the Electoral College: He scored 337,000 more votes in Maricopa County, in Arizona, a state he carried by about 11,000 votes. He won 83,000 more votes in Atlanta’s Fulton County, on his way to carrying Georgia by just under 12,000 votes. And he won the four counties that surround Philadelphia with a combined 170,000 more votes than did Clinton, more than twice his overall margin of victory in Pennsylvania.

At the same time, Trump’s raw vote total grew by more than 100,000 votes in nine counties, only two of which — Harris County, Texas, and Miami-Dade, Fla. — are in states he won. Trump earned a greater number of new votes than did Biden in only one of those large counties, Miami-Dade.

Trump’s campaign made substantial inroads among voters in Texas’s Rio Grande Valley and in areas of the Lone Star State farther from the border. Among the 24 counties where Trump’s two-party vote share increased the most between 2016 and 2020, all but three were in Texas.

Biden’s biggest improvements were in mid-size to larger counties where his campaign turned out the most new voters — including Henry, Forsyth, Rockdale and Douglas counties, all of which ring Atlanta; Collin and Denton counties, north of the Dallas Metroplex; Hamilton Co., north of Indianapolis; and El Paso County, home of Colorado Springs, Colo.

The results illustrate growing blue islands in a sea of rural red, political demographers said, as Democratic bastions in big cities radiated out into suburban and exurban counties. While the census showed rural America shrinking to a new low, the election results showed that those who remain are increasingly conservative — or at least increasingly loyal to Trump.

“We talk about demographic destiny. I think also we need to talk about geographic destiny, and that urbanization is still increasing in this country and it bodes well for Democrats in terms of pure numbers,” said Michael Bitzer, a political scientist at Catawba College in North Carolina. “The problem becomes, are they too sorted into those urban counties when things like redistricting comes around?”

Population trends show that, barring a substantial effort by Republicans to make inroads among minority voters, Democrats stand poised to gain clout in many statewide elections. Twenty-one states now have populations under 18 that are majority-minority, at a time when Democrats are sweeping up the vast majority of the nonwhite vote.

“We have a declining child population and also the first child population that is minority white,” Frey said. “Another way of thinking about the future is that the voting population will become increasingly diverse.”

But demographic sorting is a major factor in slowing the political shift between increasingly rural Republicans and increasingly urban Democrats, both Frey and Bitzer said. While Democrats may earn more votes overall, their votes are more geographically centered in one place, making it more difficult for mapmakers to spread their votes evenly between districts — and, conversely, making it easier for Republican cartographers to pack Democrats into concentrated districts.

“At a statewide level, [population growth] certainly helps Democrats, just because numbers are votes,” Bitzer said. “The dynamic particularly for state houses and the U.S. House, particularly in states where Republicans control [the legislature], they can maybe ease the pain somewhat of that shift just through redistricting.”

But the increasing diversity of a younger America, and the increasing homogeneity of Trump’s coalition, is likely to force a reckoning for Republicans who are looking for a post-Trump path back to national power — especially if those voters who turned out to vote for Trump, and only Trump, stay on the sidelines in the future.

“They’re up against demography that’s changing those areas, and they can only do it for so long. These census numbers make that pretty clear,” Frey said. “Politicians should be going where the votes are, and eventually Republicans are going to figure that out.”