Taking a large dog to Idaho State Parks
State parks require a short leash and leave off-leash space to a few designated areas.

State park rules
The Idaho State Parks camping rules says dogs must be confined or on a leash of at most six feet, off-leash areas may be designated by park managers, and dogs are not allowed at Harriman State Park. The Idaho Parks and Recreation pet policy makes the same six-foot rule and bars leaving a pet unattended.
Eagle Island State Park
The Eagle Island State Park page describes a pilot program: a 212-acre dog off-leash area and designated off-leash trails, open only if the owner shows control. On trails, an unleashed dog must be within 30 feet and under voice control, and no pets are allowed on the beach or in the lake.
Farragut State Park
The Farragut State Park page says dogs must be confined or on a leash of six feet or less and never left unattended, and that pets are not allowed in the Beaver Bay beach area.
What it says about the dog
Off-leash rules assume you can recall the dog at any time. Ask any provider to prove that control in public.
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