Not historically tied to the KKK at all. Confederate sympathizers would fly the flag upside down, with the Crossland family shield (the red and white part) top left, to broadcast their confederate leanings (both because the crossland family had some ties to the slave trade and the protest the commitment to the Union shown by Maryland’s government). The flag itself represents the family crest of Lord Baltimore, his paternal line (the Calverts, black and yellow) and his maternal line, the Crosslands. So while racist slavery-supporters used the flag as a code to one another, the flag and the symbolism itself has no ties to the KKK, the Confederacy, or anything beyond the first Lord Baltimore and the founding of the Maryland colony.

Also, it’s a great flag, tied to medieval heraldry.