President Calvin Coolidge cracked a rare smile when he stepped out of his car and into a thunderous throng of more than 60,000 people jammed into the Minnesota State Fair grandstand.

Longtime Secret Service agents said the crowd, which some estimated closer to 100,000, might have been the largest to "ever welcome a President of the United States or any other public man," according to a front-page story in the Boston Globe.

"As soon as the President's car came into sight, the occupants of the grandstand set up a mighty cheer, the kind of cheer that would have induced Theodore Roosevelt to stand up and wave his hat and arms," the Boston reporter wrote. "But the calm Coolidge is never spectacular and he merely bowed and smiled at the deafening roar."

A not-too-distant memory might have triggered his grin.

Three years earlier, at the same Minnesota grandstand, the then-vice president was roundly booed during a hot-weather speech backing the failed re-election bid of Minnesota Sen. Frank Kellogg.

In between the two polar receptions, President Warren Harding had suddenly died, elevating Coolidge to the presidency. Kellogg was now his secretary of state — and the Coolidges' host in his St. Paul mansion at 633 Fairmount Av.

Coolidge and his wife, Grace, spent June 8, 1925, in the Twin Cities to celebrate the 100th anniversary of the first Norwegian immigrants' arrival in America. The four-day Norse-American Centennial was a big deal.

Norway's prime minister was on hand. So was a blimp. Among the guests: a retired minister from Chicago, whose mother was born aboard the Norwegian sloop Restaurationen before it docked in New York in 1825.

WCCO Radio, not yet three years old, broadcast Coolidge's 45-minute speech "on a wave-length of 416.4 meters."

Thousands of schoolkids lined the streets for 10 miles between St. Paul and a Nicollet Hotel luncheon — "for block after block, people were massed 10 deep," the Boston newspaper reported. "Minneapolis … not to be outdone by its hated rival, St. Paul, turned out even larger numbers."

At one point, a children's chorus, decked out in blue and white, formed a Norwegian flag before turning their outfits inside out to display the Stars and Stripes.

There was a full-size replica of Leif Erikson's ship, and the crowd went wild when Coolidge declared that Erikson, not Christopher Columbus, first discovered America.

Lost among all the grand gestures at the Norse-American Centennial was a simple act from Coolidge.

The 30th U.S. president autographed a couple sheets of special postage stamps issued to commemorate the 100th anniversary of the Norwegian sloop's arrival. They were postmarked June 6, 1925 — the day the Norse-American celebration opened.

Coolidge started collecting stamps as a child in Vermont in the late 1800s. When his prominence grew, he often gave autographed stamp sheets as gifts.

This coming Tuesday, June 25, those two 100-stamp sheets of Coolidge-signed 2-cent and 5-cent stamps will be auctioned off among a series of 20 items from the 1925 Twin Cities Norse-American event.

When W. Irving Glover, the nation's third assistant postmaster general, announced the special stamps would go on sale in 1925, he picked four Minnesota post offices — Minneapolis, St. Paul, Benson and Northfield — among seven first-day sales venues.

Stamp collecting experts, formally known as philatelists, say the rare sheets could fetch $4,000 combined, while the entire series of 1925 Norse-American Centennial relics could be worth $40,000.

"Once in a very great while a collection comes to market that inspires us," said David Coogle, a co-owner of Connecticut-based Kelleher Auctions, which dates to 1885 and calls itself "America's Oldest Philatelic Auction House."

Hard-core stamp collectors can check out auction details at: tinyurl.com/1925stamps or Kelleher­Auctions.com. For the rest of us, the back story packs plenty of intrigue.

Coolidge originally gave the two sheets of 1925 stamps he signed in Minnesota to one of his speechwriters, Stuart Crawford.

When Coolidge died of a heart attack at 60 in 1933, Crawford gave the autographed "panes" to Coolidge's stamp-collecting nephew, Henry Woodward, who had inherited other portions of his uncle's extensive collection.

When Woodward died in 1956, his widow sold the entire collection, including the two autographed sheets. They bounced around until a collector, who has requested anonymity, bought them in 1980 from a New York antiques broker who found them at an estate sale. The anonymous collector locked them in his vault for decades.

The stamp collection was "tirelessly assembled over six decades by a collector ... who possessed two key collector traits, financial resources and an insatiable appetite," Coogle said.

Curt Brown's tales about Minnesota's history appear each Sunday. Readers can send him ideas at mnhistory@startribune.com. His latest book looks at 1918 Minnesota, when flu, war and fires converged: strib.mn/MN1918.