Bob Knutson of Granite Falls never said much. Out loud, anyway.

Knutson grew up the 10th of 14 kids on a western Minnesota farm, and turned 18 at the Depression's outset. There wasn't enough money to pay for college, but he built a successful plumbing and heating business along the Minnesota River and was elected mayor of Granite Falls in 1954.

"We rarely, if ever, had a conversation," said his daughter, Dorothy Ellerbroek, a nurse in Waconia. "He was an introvert and quite shy. And back in decades gone by, it wasn't customary for much personal conversation in our family."

That makes Knutson no different from countless Minnesota dads descended from taciturn Norwegian stock. But Ellerbroek has another theory for his laconic nature.

"Bob weighed 14 pounds at birth and cried for the first nine months of his life," she said. "His fussiness alienated him from all his siblings. Bob learned from an early age that it got him nowhere to verbalize his thoughts, so consequently he was quite close-mouthed throughout the rest of his life."

More than 30 years after his death in 1985 from lung cancer at the age of 73, the reticent plumber from Granite Falls lives on in an old-school way: his boyhood diary and the letters he wrote as an adult.

Knutson wrote in his diary about farm chores; later on, when phone calls were reserved for emergencies, he'd type letters on his Underwood manual. He'd often use carbon paper to make copies for his siblings.

The letters discussed ordinary moments and were "liberally interspersed with wry humor," his daughter said, along with Bible verses and literary quotes. She said they give her "insight into this quiet man. Through the letters … I have come to know and understand my dad better."

For those who never knew Knutson, the letters provide an intimate glimpse at 20th-century, small-town Minnesota through the eyes of a farm kid-turned-plumber who grew into his 44-inch waist, chewed unlit cigars and washed up with Lava at night.

The earliest surviving Knutson letter comes from the early 1920s when Bob was about 11 and writing to his brother Cyrus, who was teaching school in the Philippines.

He also kept a diary at that young age and wrote about how "Pa" and his older brothers had gone to the Larson place to "fire up the steam engine and thresh oats," while he was directed to stay back, hitch up horses Teddy and Polly and "cut the alfalfa meadow west of the crick."

He wrote as if he were in a play: "Bobby: But can't I go over and play with Freddie and Harold today and do the mowing tomorrow? (A short pause while eyes meet) O.K. I better go to the barn and harness up."

He continued, "I'll be glad when I get big enough to be my own boss," and described how "the monotony of riding this mower is interrupted by chasing gophers, young cottontail rabbits and by eating wild grapes hanging on the fences.

"I can see the black smoke from the steam engine and the wind carries the dust and the chaff above the trees … " he wrote. "It must be 10:45 a.m. for here comes the passenger train. The eyes follow it until it is out of sight. Then the ears listen for the distant whistle. Just four more rounds with the mower and I can quit for dinner."

Nearly 50 years later, when the Minnesota River spilled its banks and threatened the Knutson Brothers plumbing office in Granite Falls, Bob wrote about the sunny Easter Sunday in 1969 that "caused quite a heavy snow melt."

He drove 60 miles upriver "to assess water conditions … and what I saw frightened me," he wrote in April 1969. "All the ditches, draws, meadows and fields were rushing streams of cold black water."

They'd been planning for potential flooding for six weeks and had surrounded their shop with barriers and sandbags, rigging up pumps to suck up seepage.

"They closed the liquor store and all taverns in town, and put every able-bodied person to work," he wrote. "Those unwilling to help with flood relief were run out of town."

With water climbing 3 inches an hour, they realized the building couldn't handle the pressure, so they flooded the basement after protecting business records and equipment "while wearing chest-high waders." Shop doors were removed "so that they wouldn't slam shut and trap anyone inside."

Within 48 hours, the river had climbed 96 inches at the shop, but "the building withstood the onslaught."

Eight years later in 1977, Knutson wrote a piece "to be read with the nasal twang of a Southern Circus barker" for his big family's reunion — a tradition he started in the 1950s that continues to this day.

"Permit me to call your attention to the ring where the Knutsons are milling around as thick as blackbirds in a field of North Dakota sunflowers," he wrote.

He went on to discuss how his parents, Oscar Knutson and Mina Larson, "heard the admonition to be fruitful and multiply, replenish the earth … and accentuated by the universal urge to mate, this fine couple set about to accomplish the task by themselves. … As the 20th Century was ushered in, they had a good start … but did not relax their zeal to press on."

Forty years later, Knutson's daughter cherishes the quiet plumber's written words. "I feel his presence," she said, "when I touch the pages."

She recently read his 1969 flood report to her 18-year-old grandson, an aspiring engineer — passing "the wisdom of my Dad ... to the next generation."

Curt Brown's tales about Minnesota's history appear each Sunday. Readers can send him ideas and suggestions at mnhistory@startribune.com. A collection of his columns is available as the e-book "Frozen in History" at startribune.com/ebooks.