The old times used to say that locust would last 100 years longer than stone when placed on the ground. Of course that was an exaggeration but here is a link that discusses how long the wood will last. The article state the that poles made from locust and they have lasted 150 years and are still standing.0,000 black locust trees. No thorns on the trunks. Just smaller ones on the branches. Never

Why Black Locust Wood is a Superior Rot-Resistant Alternative to Treated Lumber
Black locust wood is naturally rot-resistant, durable, and insect-repelling, making it a superior, eco-friendly alternative to chemically treated lumber for fencing, decking, and outdoor structures.
