Green's Cave

Useful Information

Location: Meramec State Park. 30 minutes south of St. Louis, take I-44 West, then south on exit 233.
Open: No restrictions.
Fee: free.
Classification: SpeleologyKarst Cave ExplainCaves With Tallest Cave Entrances, Emenience Dolomite.
Light: bring torch
Dimension: Portal: W=33 m, H=28 m.
Guided tours:
Bibliography: Berton Roueché (1985): Sea to Shining Sea, containing the story Countryside about the Meramec river valley and its caves.
As far as we know this information was accurate when it was published (see years in brackets), but may have changed since then.
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1810 to 1820 used for gunpowder production.
1978 planned dam cancelled by vote.


Green's Cave is on Meramec State Park property, not far from Meramec Caverns. This park has an area of 27 km² and contains 43 caves. It is called the most cavernous piece of real estate in Missouri.

The cave entrance is 28 m high and 33 m wide, and said to be the largest cave opening east of the Mississippi. At least we found this superlative on a website. Funny fact: Green's Cave is located west of the Mississippi. This seems to be one of those superlatives... For more on this topic see ExplainCaves With Tallest Cave Entrances

Green's Cave is named after the Green Family, who once owned the property with the cave. The cave had numerous owners until it was acquired by the Army Corps of Engineers, who was attempting to build a USD 100 million dam right here. The overlook above the cave would have been a 3 m drop into 28 m deep water, if the dam had been built. However, it is not really a good idea to build a dam in a karst area. Water tends to flow away through caves and it is rather likely, the lake would never have filled completely.

Green's Cave is a wild cave, it is possible to visit it anyway, at least the entrance region. There is normally a Park Ranger who makes shure careless floaters do not enter the cave beyond the reach of daylight. There are three ways to reach the cave:

  1. Float up the Meramec river from Sappington Bridge 4.1 km.
  2. Hike in from Hamilton Iron Works.
  3. Hike in from Hwy 185.