Last Wednesday, I broke the news to Heather Cox Richardson that she was the most successful individual author of a paid publication on the breakout newsletter platform Substack.

Early that morning, she had posted that day’s installment of “Letters From an American” to Facebook, quickly garnering more than 50,000 reactions and then, at 2:14 a.m., she emailed it to about 350,000 people. She summarized, as she always does, the events of the day, and her 1,120 words covered a bipartisan vote on a spending measure, President Trump’s surprise attack on that bill, and a wave of presidential pardons. Her voice was, as it always is, calm, at a slight distance from the moment: “Normally, pardons go through the Justice Department, reviewed by the pardon attorney there, but the president has the right to act without consulting the Department of Justice,” she wrote. “He has done so.”

The news of her ranking seemed to startle Dr. Richardson, who in her day job is a professor of 19th century American history at Boston College. The Substack leader board, a subject of fascination among media insiders, is a long way from her life on a Maine peninsula — particularly as the pandemic has ended her commute — that seems drawn from the era she studies. On our Zoom chat, she sat under a portrait that appeared as if it could be her in period costume, but is, in fact, her great-great-grandmother, who lived in the same fishing village, population a bit over 600.

She says she tries not to think too much about the size of her audience because that would be paralyzing, and instead often thinks of what she’s writing as a useful primary document for some future version of her historian self. But there was no ignoring her metrics when her accountant told her how much she would owe in taxes this year, and, by extension, just how much revenue her unexpected success had brought. By my conservative estimate based on public and private Substack figures, the $5 monthly subscriptions to participate in her comments section are on track to bring in more than a million dollars a year, a figure she ascribes to this moment in history.

“We’re in an inflection moment of American politics, and one of the things that happens in that moment is that a lot of people get involved in politics again,” she said.

Many of those newly energized Americans are women around Dr. Richardson’s age, 58, and they form the bulk of her audience. She’s writing for people who want to leave an article feeling “smarter not dumber,” she says, and who don’t want to learn about the events of the day through the panicked channels of cable news and Twitter, but calmly situated in the long sweep of American history and values.

Dr. Richardson’s focus on straightforward explanations to a mass audience comes as much of the American media is going in the opposite direction, driven by the incentives of subscription economics that push newspapers, magazines, and cable channels alike toward super-serving subscribers, making you feel as if you’re on the right team, part of the right faction, at least a member of the right community. She’s not the only one to have realized that a lot of people feel left out of the media conversation. Many of the most interesting efforts in journalism in 2021, some of them nonprofit organizations inspired by last summer’s protests over racism, will be trying to reach people who are not part of that in-group chat. One new nonprofit, Capital B, plans to talk to Black audiences, while another well-regarded model is Detroit’s Outlier Media, which is relentlessly local and often delivered by text message. For Dr. Richardson’s audience, it’s an intimate connection. She spends hours a day answering emails from readers. She spent most of Saturday sending thank-you notes for Christmas presents.