“That’s a big problem.” Mike Jastremski was concerned. We were looking down from Route 4 at the Furnace Brook fish ladder. In the fish channel was the piece of a tree—about 11-feet long and eight inches in diameter. “Heavy. Waterlogged. Gotta get it out of there.” Mike is HVA’s “watershed conservation director”—burly, bearded, and agile.

Furnace Brook is, according to Starr’s history, “the largest stream entirely within the township.” It is a spreading tree of tributaries that eventually funnel down to its opening into the Housatonic. The ladder is about a thousand feet up from the mouth.

Earlier in the day, Mike had led me to the site of the furnace itself (upstream from the ladder) and handed me— somewhat tottery and in borrowed hip boots—down the steep and slaggy slope to the water running dark and foaming white over the stones. I’d planned to wade there, but he said, diplomatically, “Well, the flow is a bit strong today; we don’t need to go in.”

On the slope by the brook, I had picked up a few brightly colored pieces of slag. Slag is the scum from iron processing, but to call it “scum” does not give credit to its beauty: shiny jagged pieces of midnight blues, blacks, deep purples, and greens. The slag’s color indicates the efficiency of the furnace; solid green proves proper amounts of ingredients: ore, charcoal, lime, and blast.

On the tall opposite bank are stone remains of the 1833 Cornwall Bridge Iron Company furnace wall which was once 30 or more feet high. (A hill by a furnace slopes usefully from above, so the trestle can send materials—charcoal, lime and ore—down into the furnace to meet the blast.)

In the early 19th century, brooks served many purposes. Furnace Brook had, for example (according to Allen’s Cornwall in 1801) many “works“: One gristmill, one mill to grind bark for a tannery, several sawmills, one forge and “one mill to grind Wheat, Corn &c.” The ore, at that time, came from neighboring Salisbury and Sharon. But by the end of the century, industries turned to coal and electricity for power. The furnace closed in about 1892. And by then, of course, most of the trees were gone. Furnaces eat about 1,200 bushels of charcoal a day. But now the brook runs free.

Nonetheless, trout had a hard time after a 1992 road repair obstructed fish from moving upstream. HVA installed a fish ladder in 1995; it was replaced by the current more permanent one in 2014. A constant problem is road runoff from Route 4 which dumps bad stuff into the brook and—particularly in summer—warms the water. Trout like it cold, and, for the most part, they benefit from the shade of hemlocks in the ravine.

Gone is Connecticut’s fish opening day (traditionally the second Saturday in April), when cars lined the road and VFW fish fries followed. But the fish are still there, thanks to the ladder which supports spawning migrations and to DEEP stocking of brown trout. Furnace Brook is a “Wild Trout Management Area Class 2,” one of only two such streams in the state; it is a critically important thermal refuge. It supports more trout during summer months than any other thermal refuge. And now it is also swaddled in the Cornwall Conservation Trust’s 107-acre preserve.

So let’s hear it for this most multi-talented brook, its friends, and for the return of the natives.

—Ella Clark

📸: Pictured above, Furnace Brook, by Lazlo Gyorsok

Furnace Brook Uniqueness:


  • Entire stream from the confluence with the Hous is a Wild Trout Management Area Class 2 (WTMA 2). There are only 2 of these in the state.
  • WTMA 2 designation means the brook supports some natural reproduction These streams do not have enough natural reproduction to support fishing pressure; however, through the stocking of juvenile brown trout (fry) angling is supported.
  • Often referred to as a “put-grow-and take fishery” meaning juvenile fish are stocked with the expectation they will grow to catchable size and then caught by anglers.
  • Open to fishing year-round.
  • Daily limit of 2 trout with minimum length of 12 inches. Harvest is allowed from 6:00 am on the second Saturday of April until the last day of February. Catch and release only March 1 to 6:00 am on the second Saturday of April (historic “Opening Day”)
  • Link to WTMA information


  • Historically stocked with ~10,000 brown trout fry during April
  • No longer stocked with adults
  • Currently a 3-year moratorium on fry stocking, as the Fisheries Division is evaluating the success of the fry stocking using various sampling techniques.
  • Results will inform next steps regarding trout stocking


  • Coldwater tribuatary to the Housatonic
  • Critically important thermal Refuge near the confluence with the Hous
  • From June 15th to September 15th NO FISHING within 100’ of brook to protect congregations of trout seeing refuge from elevated temperatures in the mainstem of the Hous
  • Furnace Brook supports the most trout during the warm summer months than any other thermal refuge (Mill Brook, Powerhouse Brook, Kent Falls Brook)
  • Thermal refuge physically enhanced each year by the Fisheries Division (pictures attached)
  • Fish ladder under Rte. 4 to support spawning migrations of trout up into the brook
  • Incredible public access along Rte. 4 with pull-offs, picnic areas and public land
  • Forested scenery offering a remote fishing experience in NW CT

Link to Statewide Wild Trout Management Plan

📸: Lazlo Gyorsok

📸: Lazlo Gyorsok

📸: Lazlo Gyorsok

📸: Lazlo Gyorsok

📸: Mike Jastremski

📸: Mike Jastremski

📸: Mike Jastremski

📸: Cornwall Bridge Furnace, Cornwall, ca. 1880 - provided by the Salisbury Association archives