We present spectroscopic redshifts of {\text{}}{S}870μ
{{m}} ≳ 2 mJy submillimeter galaxies (SMGs), which have been
identified from the ALMA follow-up observations of 870 μm detected
sources in the Extended Chandra Deep Field South (the ALMA-LESS survey).
We derive spectroscopic redshifts for 52 SMGs, with a median of z = 2.4
± 0.1. However, the distribution features a high-redshift tail,
with ˜23% of the SMGs at z≥slant 3. Spectral diagnostics suggest
that the SMGs are young starbursts, and the velocity offsets between the
nebular emission and UV ISM absorption lines suggest that many are
driving winds, with velocity offsets of up to 2000 km
s-1. Using the spectroscopic redshifts and the
extensive UV-to-radio photometry in this field, we produce optimized
spectral energy distributions (SEDs) using Magphys, and use the SEDs to
infer a median stellar mass of {M}\star = (6 ±
1)× 1010 M {}⊙ for our SMGs with
spectroscopic redshift. By combining these stellar masses with the star
formation rates (measured from the far-infrared SEDs), we show that SMGs
(on average) lie a factor of ˜5 above the so-called “main
sequence” at z˜ 2. We provide this library of 52 template fits
with robust and uniquely well-sampled SEDs as a resource for future
studies of SMGs, and also release the spectroscopic catalog of ˜2000
(mostly infrared-selected) galaxies targeted as part of the
spectroscopic campaign.