Theater is by nature ephemeral. Companies endure or vanish, and the shows they put on open and close, living on only in the memories of the artists and audiences who shared each production.

Lately in South Florida, theater has felt a little too ephemeral. This dispiriting trend began with the shuttering of the debt-burdened Coconut Grove Playhouse at the end of its 50th anniversary season in 2006. In June 2011, Florida Stage abruptly went belly up, massive debt again the problem. Last March, Davie’s smaller Promethean Theatre shut down after eight seasons.

And now, another major loss. On Tuesday, the Caldwell Theatre Company’s $10 million Count de Hoernle Theatre on Federal Highway in Boca Raton will be sold in an online foreclosure auction. The theater building, which isn’t quite five years old, sits on 1.5 acres and is being sold to satisfy a $6.75 million foreclosure judgment in favor of mortage holder Legacy Bank of Florida.

In truth, the Caldwell ended its 37-year run as an important, influential South Florida theater company after its production of the musical Working closed on April 1. Sure, there were hopes that donors keep one of the region’s oldest companies from disappearing. But that didn’t happen. The Caldwell is toast. And that matters.

Artistic director Michael Hall and designer Frank Bennett started the Caldwell in 1975. Rubbermaid founder James R. Caldwell had retired to Boca Raton, and he persuaded Hall to relocate to a place which then had very little in the way of professional theater.

Hall retired as artistic director in 2009. Responding to questions via email, he looks back with pride, nostalgia and the tiniest hint of sorrow when asked about his artistic offspring.

From the beginning, he and Bennett (joined by company manager Patricia Burdett) aimed to create ensemble productions, with Bennett contributing striking sets, costumes and props with perfect period detail. Producing in four different theater spaces throughout the theater’s history, Hall observes, “we weren’t afraid to tackle large-cast period plays like Somerset Maugham’s Our Betters in 1977, and later The Little Foxes, The Royal Family, A Few Good Men and Fortune’s Fool … we put a lot of theater folks to work.”

In fact, the Caldwell became a vital employer and nurturer of South Florida theater talent. Those American theater classics, later mixed with cutting-edge contemporary plays and some new works, provided decent pay for union actors and designers while building a loyal audience. Actors Barbara Bradshaw, Peter Haig, Pat Nesbit, John Felix, Tom Wahl, Elizabeth Dimon, Kim Cozort, Kenneth Kay, Terry Hardcastle, Dennis Creaghan, Harriet Oser, Angie Radosh and so many more became part of a loose-knit Caldwell rep company, appearing in play after play.

Bradshaw, a multiple Carbonell winner, was with the Caldwell from the beginning, becoming its frequent leading lady. Of Hall she says, “If I ever had a mentor that I owe everything to, from the time I was 23, it’s Michael Hall.”

When he thought she was ready, Hall gave her lead roles in The Heiress, Candida, Hedda Gabler, The Philadelphia Story, The Rainmaker and other theater classics.

“I did every single show for the first four or five seasons,” she says. “What it was, in many respects, was a library theater of the great plays.”