Grin, a privacy coin built with MimbleWimble, successfully hard forked for the first time at block height 262,080. Wednesday's fork is the first of four forks designed to execute within the first two years of Grin's existence at block heights 262,080, 524,160, 786,240, and 1,048,320. The network upgrade at block height 262,080 adjusted the protocol's existing proof of work and made minor changes to the node API in addition to a few Grin wallet changes, which can be read in detail here.