On November 23, the Maryland Republican Party rejected a resolution to allow independent voters to vote in the Republican 2014 primary. See this Washington Post story. The party will reconsider the idea in the future, and might open its 2016 primary.

The Maryland Republican Party already let independent voters vote in its 2000 primary, but afterwards, the party returned to a closed primary. The article does not mention the 2000 experiment. Thanks to Nancy Hanks for the link.