We present new optical and near-IR spectroscopy as well as new high dynamic range, arcsecond-resolution VLA radio maps of BL Lacs from the complete radio-selected “1 Jansky ” (1Jy) sample (RBLs) for which such data were not previously available. Redshift information is now available for all but six of the 37 BL Lacs in the 1Jy sample. Of the 31 with redshift information, four redshifts are only minimum values based upon absorption lines and four other objects have uncertain redshifts based upon the detection of only a single emission line. Unlike BL Lacs from the complete X-ray-selected Einstein Medium Sensitivity Survey (EMSS) sample (XBLs), most RBLs possess weak but moderately luminous emission lines. The emission-line luminosities of RBLs are several orders of magnitude lower than flat-spectrum radio quasars (FSRQs); however, there is significant overlap in the luminosity distributions of the two classes. All but one object in the 1Jy sample has now been observed with the VLA; and extended flux was detected for all but three of the observed objects. Whereas nearly all XBLs have extended power levels consistent with FR–1s, more than half of the RBLs have extended radio power levels too luminous to be beamed FR–1 radio galaxies. In fact, we find evidence for and examples of three distinct mechanisms for creating the BL Lac phenomenon in the 1Jy sample: beamed FR–1s, beamed FR–2s and possibly a few gravitationally-lensed quasars. The 〈V/Vmax 〉 determined for the 1Jy sample is 0.614 ± 0.047, which i
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