pruneblockchain "height"

The pruneblockchain RPC prunes the blockchain up to a specified height or timestamp.

*bitcoin-cli help pruneblockchain

pruneblockchain

Arguments:
1. "height"       (numeric, required) The block height to prune up to. May be set to a discrete height, or a unix timestamp
                  to prune blocks whose block time is at least 2 hours older than the provided timestamp.

Result:
n    (numeric) Height of the last block pruned.

Examples:
> bitcoin-cli pruneblockchain 1000
> curl --user myusername --data-binary '{"jsonrpc": "1.0", "id":"curltest", "method": "pruneblockchain", "params": [1000] }' -H 'content-type: text/plain;' http://127.0.0.1:8332/