Finches chirping from cages and angel fish swimming nearby in bubbling aquariums echo from a bygone era at Sonnen's Pet Shop in downtown St. Paul.

The 600-square-foot, ground-level shop oozes history at 408 St. Peter St. in the Hamm Building. The six-story structure — a spectacular swirl of beer money, marble and terra cotta — celebrates its 100th birthday Sept. 12 with a public bash featuring live music, actors in 1919 garb and food from its swank restaurant tenant, Meritage.

Louis Sonnen moved his West 7th Street pet shop into the Meritage space in 1936. Five years later, when Pearl Harbor was attacked, he shifted across the Hamm Building's opulent lobby to the shop's current location.

"He wanted a smaller space because he figured ­he'd be away fighting for a few years," Louis' son, David ­Sonnen, 75, said from his perch behind the pet shop counter. David began working here for his father as a teenager in the mid-1950s.

Flat feet ultimately kept Louis home. The draft board twice rejected his enlistment — keeping alive what's now an 88-year run with a Sonnen working amid the bird cages and tropical aquariums. The business actually started in 1892, and its 127 years of continuous operation make it one of downtown St. Paul's oldest retail shops.

David Sonnen pulled a small yellow can of Heger's Flea Powder off a shelf the other day. Its label assured owners of itchy dogs that no metal was used in the powder that could divert resources from the war effort.

Hamm Building, St. Paul, 1922-25

"That would be World War I," David Sonnen said. The flea powder carries the name of German émigré Herman Heger, who started the shop before peddling his own brand of flea powder.

The son of a Rice Street druggist, Louis Sonnen was born in 1911 and married ­Rosabelle Feyereisen in 1940. His German-born grandparents settled in New Ulm in the 1850s, fleeing the U.S.-Dakota War in 1862 for the safety of St. Paul. Sonnens have been in St. Paul ever since, the family mushrooming with Louis and Rosabelle's five kids, more than a dozen grandchildren and countless cousins and descendants.

"They still have the family's shotgun down in New Ulm," said John Paul Sonnen, 40, David's son and Louis' grandson. John and his aunt, Susie Sonnen, have carefully chronicled the history of their quirky family business.

Louis started working at the shop in 1931 for $6 a week, quitting after one day because he couldn't stand the stench of the dogs and cats.

"This was right at the start of the Great Depression," David Sonnen said. "Times were tough and work was scarce."

A widow who owned the shop wooed Louis back for $15 a week, selling him the business when he was 22 in 1934. Only the shop's third owner, Louis quickly changed the name to Sonnen's Pet Shop and got rid of the dogs and cats to focus on fish, birds and small gifts — not to mention the occasional rabbit, turtle and hamster. Two years into his ownership, he moved the shop into the Hamm Building.

"When he bought it in the Depression, things were tough, but in the 1940s and '50s, people had money and business was good," David Sonnen said. "I remember when the elevators in the lobby opened and people streamed out to the crowded sidewalks."

Today, with St. Peter Street dug up for new water pipes and Dayton's downtown department store long gone, "no one comes down," David Sonnen said with a shrug.

Online buying and mega-pet stores haven't helped, but he thinks the business' woes are more linked to changing habits. The hobby of keeping tropical fish and caged birds disappeared when computers and smartphones became ubiquitous.

"Kids stopped wanting aquariums and just wanted electronic games and computer stuff," said David Sonnen, who has no plans to retire even though he's 75. His dad, Louis, lived until he was 89, dying in 2001. When he wasn't selling pets, Louis played the organ for six decades at the twin-spired Church of the Assumption a few blocks away.

Despite long life spans for the business and its third owner, David Sonnen said "there's no way" a next generation could take over and "make a decent living."

His son, John, acknowledges "the end is near — the days of downtown boutique shops like this one are long gone."

So the family celebrates its long run in the Hamm Building with stories — like the time escaped jewelry store bandits got in a shootout with cops in the lobby in 1985, leaving one robber dead. Bullet holes can still be found on a lobby wall.

"I was standing right here, weighing something on this scale," David Sonnen said from a back-office desk, pointing through a window with a view of the lobby. "I locked the doors."

If only it were that easy to protect their old family business from the passage of time.

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