Thacher offers a unique experience for Northeastern climbers as the only limestone cliff in the region. Europe and the American West have plenty of limestone climbing areas but this is the only sizeable limestone sport climbing in the Northeast US. The area provides plenty of challenging climbs on smooth crimpy faces and steep cave formations. Rock texture ranges from smooth to rough textured pocketed areas. Wear a helmet as the area is new and there is choss in spots.


Thacher’s rock tells a tail of ancient seas filled with life. The eurypterid was a fearsome sea scorpion, sometimes bigger than a human (470-248 Million years ago).

Science: There are two layers of limestone at Thacher: the Manlius and the Coeymans. Like limestone in many western climbing areas the rock is filled with fossils including crinoids, trilobites, brachiopods and the fascinating giant sea scorpion. Thacher’s rock was important in the history of geological studies and was featured in textbooks since the 1800s.

The limestone at Thacher begins with the Manlius limestone and the beginning of the Devonian era. As you climb higher you will see the rock grow richer with fossils. The richest rock of all for fossils is the Becraft Limestone. This layer is not part of the main cliffs and is found at higher elevations in the park. Despite this you can still expect yourself to be crimping on crinoids on most routes.

Finger pockets on the left and right of this ancient coral in the middle of a route at the Fossil Wall at Thacher.
A 2″ Trylobyte is in this crack along this beginner climb.

Sport Climbing: “Sport” Climbing refers to climbing in which expansion bolts or glue-ins are used as anchors. Sport climbing is more suitable than trad climbing on softer rocks. In sport climbing the climber hikes into the bottom and climbs up to a top anchor. At Thacher rappelling and topping out will not be permitted. See more rules here.


Features: Thacher’s rock has a few distinct shapes and features. Certain areas resemble giant onions with rounded shapes featuring hard bulge climbs on the bottom half. There are also plenty of smooth hard walls to climb. Most of these smooth lines average 5.10+. The crack sizes on average are perfect for the human hand and fingers. Many of the climbs at Thacher feel incredible as you are 600 feet above the Hudson valley, so you will feel the exposure despite most climbs being in the 35-50′ range. Some climbs cross both the Manlius and Coeymans layers are higher at 70-90′.

Small bed of Tropidoleptus carinatus, an orthid brachiopod of the Devonian period on the boundary between the Coeymans and Manlius limestone layers.


Limestone hardness and other properties are similar to that of concrete. Thacher climbs use a combination of glue-ins and expansion bolts as anchors and protection. Glue-ins use epoxy and are becoming a worldwide standard for use in limestone from Thailand to France. They have a longer life and are lower in visual impact. Bolting and development of routes are regulated through the TCC.

Fossil collection is illegal at Thacher and over time has a visible effect. Leave fossils in the rock for future climbers to view and enjoy.

People have been climbing Thacher’s cliffs since the Mahican Indians established hunting grounds on the lands above the cliffs. Read more on the climbing history here.

See photos of people climbing at Thacher here:

About the effort to legalize ice climbing at Thacher

Visit Thacher – costs, permits, camping options and more