We report spectroscopic measurements of stars in the recently discovered young stellar association Price-Whelan 1 (PW1), which was found in the vicinity of the Leading Arm (LA) of the Magellanic Stream (MS). We obtained Magellan+MIKE high-resolution spectra of the 28 brightest stars in PW 1 and used The Cannon to determine their stellar parameters. We find that the mean metallicity of PW1 is [Fe/H]=-1.23 with a small scatter of 0.06dex and the mean RV is V_hel_=276.7km/s with a dispersion of 11.0km/s. Our results are consistent in T_eff_, logg, and [Fe/H] with the young and metal-poor characteristics (116Myr and [Fe/H]=-1.1) determined for PW1 from our discovery paper. We find a strong correlation between the spatial pattern of the PW1 stars and the LA II gas with an offset of -10.15{deg} in L_MS_ and +1.55{deg} in B_MS_. The similarity in metallicity, velocity, and spatial patterns indicates that PW1 likely originated in LA II. We find that the spatial and kinematic separation between LA II and PW1 can be explained by ram pressure from Milky Way (MW) gas. Using orbit integrations that account for the LMC and MW halo and outer disk gas, we constrain the halo gas density at the orbital pericenter of PW1 to be n_halo_(17kpc)=2.7_-2.0_^+3.4^x10^-3^atoms/cm^3^ and the disk gas density at the midplane at 20kpc to be n_disk_(20kpc,0)=6.0_-2.0_^+1.5^x10^-2^atoms/cm^3^. We, therefore, conclude that PW 1 formed from the LA II of the MS, making it a powerful constraint on the MW-Magellanic interaction.
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