  Wide-field searches for young stellar objects (YSOs) can place useful
constraints on the prevalence of clustered versus distributed star formation.
The Spitzer/IRAC Candidate YSO (SPICY) catalog is one of the largest
compilations of such objects (~120,000 candidates in the Galactic midplane).
Many SPICY candidates are spatially clustered, but, perhaps surprisingly,
approximately half the candidates appear spatially distributed. To better
characterize this unexpected population and confirm its nature, we obtained
Palomar/DBSP spectroscopy for 26 of the optically-bright (G<15 mag) "isolated"
YSO candidates. We confirm the YSO classifications of all 26 sources based on
their positions on the Hertzsprung-Russell diagram, H and Ca II line-emission
from over half the sample, and robust detection of infrared excesses. This
implies a contamination rate of <10% for SPICY stars that meet our optical
selection criteria. Spectral types range from B4 to K3, with A-type stars most
common. Spectral energy distributions, diffuse interstellar bands, and Galactic
extinction maps indicate moderate to high extinction. Stellar masses range from
~1 to 7 $M_\odot$, and the estimated accretion rates, ranging from
$3\times10^{-8}$ to $3\times10^{-7}$ $M_\odot$ yr$^{-1}$, are typical for YSOs
in this mass range. The 3D spatial distribution of these stars, based on Gaia
astrometry, reveals that the "isolated" YSOs are not evenly distributed in the
Solar neighborhood but are concentrated in kpc-scale dusty Galactic structures
that also contain the majority of the SPICY YSO clusters. Thus, the processes
that produce large Galactic star-forming structures may yield nearly as many
distributed as clustered YSOs.
