Along with its seriffed companion Clearface, it is a member of perhaps the earliest dedicated serif+sans type series. It was first shown by ATF in 1911 [American Bulletin, May-Jun 1911].
Various digitizations exist. Linotype/Adobe’s spans five weights, Monotype’s two weights. Scangraphic’s has three weights (sold by SoftMaker as Cleargothic), URW’s additionally features a Round version. See also Brendel’s Clear Gothic (seven weights plus italics).