Alvhild Sherve of Northfield is 91, but one memory from seven decades ago remains clear as that summer day in 1945. A week shy of her 18th birthday, she'd been tromping around a field near her western Minnesota home in Madison with her high school boyfriend.

"We were barefoot for some reason," she said. "I was curious to see what a mustard plant looked like, so we came home all dirty with this big mustard plant — roots and all."

Her mother, Lyla, greeted her and was utterly embarrassed. Two guests had stopped to visit her father, Theodor Slen, a well-connected lawyer, former state legislator and Democratic National Committee member.

"Hubert and Muriel Humphrey were sitting in our house," she said. Then the mayor-elect of Minneapolis, Humphrey would take office in a week. To fill the awkward barefoot interruption, the teenager asked Humphrey if he knew what flower she had dragged home.

"He guessed it was a lady slipper — the Minnesota state flower," Sherve recalled. "We got a good laugh out of that."

Sherve is a living link to a largely forgotten but quietly influential pioneer of progressive politics in Minnesota. Given that DFLers swept statewide offices in November's election, Theodor Slen's legacy is well worth revisiting.

A grandson of Norwegian immigrants, Slen was born Oct. 15, 1885 — the oldest of three brothers in the southern Minnesota hamlet of Delavan.

In 1898, the family moved 160 miles northwest to the town of Boyd in Lac qui Parle County — which would become Slen's home county for 88 years. He was buried at Faith Cemetery in Madison at age 100 in 1986.

In between, there were stints in the Army during World War I — he was wounded in France, earning him a Purple Heart. His education took him from a Lutheran school in Madison to an oratory prize at St. Olaf College to a law degree from the University of Minnesota.

As La qui Parle County attorney during Prohibition, he joined the sheriff on enough moonshine raids that Canadian booze smugglers avoided the county.

His political arc started as a local Republican. He served as an independent in the state House from 1935-1940, but worked closely with the Farmer-Labor Party. For the next five decades, he was a Democrat — launching an unsuccessful bid for the 1940 gubernatorial nomination. He later became a judge.

"I remember our Lutheran pastor stopping by on a Sunday night to ask my father if he really was running as a Democrat for governor," Sherve said. "That was kind of unheard of back then in our area."

Minnesota politics featured three parties in the 1930s — the Republicans, the strong Farmer-Laborites and the weakening Democrats. When Harold Stassen, a 31-year-old, became governor in 1938, it revealed the decline of the Democrats and Farmer-Laborites, who were splitting votes.

One early winter day in 1941, Slen's law office phone rang in Madison. National Democratic honchos were calling from Washington. They wanted him to spearhead a big fundraising dinner in Minneapolis.

"That's ridiculous, I can't think of anyone more unqualified to handle a thing like that than I," he said, recalling the conversation in a 25-page, 1982 oral history online at tinyurl.com/TheodorSlen.

The national Democrats assured him he would get plenty of help and they wanted him to become chairman of a group aimed at merging the party with the Farmer-Laborites. President Franklin Roosevelt was part of the merger's impetus — fearing he'd lose Minnesota without it.

Humphrey is often credited with forging the merger, something former Gov. Elmer A. Benson called a "myth" and a "falsehood" in a 1980 article in Minnesota History magazine. He mentioned Slen as being an "especially" important player in the 1944 merger.

The debate over Humphrey's role played out in a series of letters to the editor in 1967, including one from Slen, who said Humphrey was a good moderator, "but he had no part in the steps taken for the new party."

Back in Northfield, Slen's 91-year-old daughter insists: "Daddy didn't like Humphrey at all" and considered him "a brash South Dakota drugstore guy."

The "enmity" that she says marked her father's relationship with Humphrey worsened when the future senator and vice president blocked Slen's appointment to become a U.S. marshal.

"That didn't register too well with me, naturally, and I have been trying to put away all bitterness ever since," Slen said in 1982. "As a good Lutheran, I … know that bitterness doesn't do any good."

He instead focused his energies on singing in his church choir and serving as Sunday school superintendent for 25 years.

Slen died on July 4, 1986, a year after he and his wife were grand marshals at Madison's centennial celebration. His town named a swimming pool park after him.

Curt Brown's tales about Minnesota's history appear each Sunday. Readers can send him ideas and suggestions at mnhistory@startribune.com.