The Letort and the Terrestrial Fly

Carlisle, Pennsylvania, is not where most people expect to find a landmark of American fly fishing. But Letort Spring Run, a small limestone stream in Cumberland County, is described by outdoor writers as the place where a generation of anglers worked out how to catch trout that were feeding on land insects, not mayflies. This tale tells what the sources say, what they leave out, and how the stream is regulated today. The fly-fishing history belongs to the anglers who lived it, and we report it as outdoor writers do: carefully, and with the gaps showing.

The story

Four outdoor-media sources, Mid Current, Flylords, Dark Skies Fly Fishing and Wikipedia, agree on the main names. Charlie Fox, Vince Marinaro and Ernie Schwiebert are credited with developing many modern flies and techniques on the Letort, using the stream as a testing ground. It is described as the birthplace of terrestrial-style dry-fly patterns, and a fly, the LeTort Hopper, is named for the stream. Marinaro, the author of A Modern Dry-Fly Code, is quoted by one fishing blog as saying the Letort “is a hard taskmaster and does not treat lightly any violation of dry fly technique.” We have not checked that quotation against his book, so treat it as the blog’s wording.

None of the sources we read gives dates for when these experiments took place. Writers say “mid-twentieth century,” and we leave it at that rather than guess a year.

The stream today

The Letort runs through Carlisle and is a tributary of the Conodoguinet Creek. A 2018 blog describes it as unstocked for decades, with wild trout, and ranks it among the most technically demanding trout streams in the country: clear water, weed beds and trout that see a lot of anglers. Local fishermen quoted in one source estimate that streamflow is about half what it was 50 years ago because of groundwater withdrawals. That is an estimate by longtime anglers, not a measurement.

On July 31, 2019, a suspected pollution event killed more than 200 wild trout in a short stretch of the stream, according to Flylords. The Pennsylvania Fish and Boat Commission and the state Department of Environmental Protection responded, and Cumberland Valley Trout Unlimited has worked on the stream for more than five decades. We describe the cause only as a suspected pollution event, because that is how the source describes it.

How it is regulated

The 2026 Pennsylvania regulations book lists a 1.71 mile section of the Letort as Catch and Release Fly-Fishing Only. It runs from 300 yards upstream of the T-481 (Bonnybrook Road) bridge downstream to the Reading Railroad bridge at the southern edge of Letort Spring Park. No trout may be killed or kept, you may use fly tackle only, no baitfish or fishbait is allowed, and you need a trout permit. Other fly-only sections in the same county include Big Spring Creek and Green Spring Creek. The 2026 DEP advisories have no entry for the Letort. Trindle Spring Run, a different stream in the same county, has one, so do not confuse them.

Why it matters to a tackle shop

Waters like the Letort ask for a light rod, a long fine leader and a quiet approach. They are where the craft of making a short, sensitive rod matters most. We say that as rod builders, not as fly-fishing authorities, because no one at BCRods has verified fly credentials to claim for the Letort itself. For the practical side of Pennsylvania’s fly-only streams, the permit, the season and the rules, see our Pennsylvania trout guide.

What we could not confirm

We did not find development dates for any of the flies or techniques. The Marinaro quotation comes from one blog. Stories of a 1981 chemical spill and ashes scattered in 1986 appear in a single blog, so we leave them out. The naming of the stream’s special-regulation program is not settled in every source, and we follow the Commission’s own book. Cumberland Valley Trout Unlimited’s history would be a better source for the restoration. If you know of one, we would like to see it. More stories are on our Pennsylvania Dock Tales page.