The young midshipman needed a date one evening while he was home from the US Naval Academy, so his younger sister paired him with a family friend who already had a crush.

Nearly eight decades later, Jimmy and Rosalynn Carter are still together in the same tiny town where they were born, grew up and had that first outing. In between, they’ve traveled the world as Naval officer and military spouse, American president and first lady, and finally as human rights and public health ambassadors.

“It’s a full partnership,” the 39th president said ahead of the couple’s 75th wedding anniversary on 7 July.

It will be another milestone for the longest-married presidential couple in American history. At 96, Carter also is the longest-lived of the 45 men who’ve served as chief executive.

“My biggest secret is to marry the right person if you want to have a long-lasting marriage,” Carter said.

The nonagenarians – she’s now 93 – offered a few other tips for an enduring bond.

“Every day there needs to be reconciliation and communication between the two spouses,” the former president said, explaining that he and Rosalynn, both devout Christians, read the Bible together aloud each night. “We don’t go to sleep with some remaining differences between us,” he said.

Still, she emphasized a caveat: “Each (person) should have some space. That’s really important.”

As first lady, Rosalynn Carter carved her own identity even as she supported her husband. Building on her predecessors’ efforts to highlight special causes, she went to work in her own East Wing office, setting a standard for first ladies by working alongside her husband’s West Wing aides on key legislation, especially dealing with health care and mental health.

Certainly, a 75-year marriage hasn’t been seamless, the couple acknowledges.

“My wife is much more political,” he said.

She interjected: “I love it. I love campaigning. I had the best time. I was in all the states in the United States. I campaigned solid every day the last time we ran.”

That didn’t help avoid a rout by Republican Ronald Reagan in 1980. But it further cemented Rosalynn – who’d originally given up her own opportunity to go to college when she married at age 18 – as equal partner to the leader of the free world. And it marked Jimmy Carter’s evolution as a spouse.

He’s since been an outspoken voice for women’s rights, including within Christianity. Carter left the Southern Baptist Convention in 2006, denouncing what he called “rigid” views that “subjugated” women in the church and in their own marriages.

The former president ratified those views again, as well as his support for the church recognizing same-sex marriage.

The Carters plan to celebrate their own marriage milestone a few days after their anniversary with a party in Plains. Decades removed from inaugural balls and state dinners, the most famous residents of Sumter County said they have mixed feelings about the spotlight.

“We have too many people invited,” Rosalynn Carter said with a laugh. “I’m actually praying for some turndowns and regrets.”