We discovered a large population of previously unknown Galactic H II regions by using the Green Bank Telescope to detect their hydrogen radio recombination line emission .
Since recombination lines are optically thin at 3 { cm } wavelength , we can detect H II regions across the entire Galactic disk .
Our targets were selected based on spatially coincident 24 \mu { m } and 21 { cm } continuum emission .
For the Galactic zone -16 \arcdeg \leq \ell \leq 67 \arcdeg and | { \it b } | \leq 1 \arcdeg we detected 602 discrete recombination line components from 448 lines of sight , 95 % of the sample targets , which more than doubles the number of known H II regions in this part of the Milky Way .
We found 25 new first quadrant nebulae with negative LSR velocities , placing them beyond the Solar orbit .
Because we can detect all nebulae inside the Solar orbit that are ionized by O-stars , the Discovery Survey targets , when combined with existing H II region catalogs , give a more accurate census of Galactic H II regions and their properties .
The distribution of H II regions across the Galactic disk shows strong , narrow ( \sim 1 kpc wide ) peaks at Galactic radii of 4.3 and 6.0 kpc .
The longitude-velocity distribution of H II regions now gives unambiguous evidence for Galactic structure , including the kinematic signatures of the radial peaks in the spatial distribution , a concentration of nebulae at the end of the Galactic Bar , and nebulae located on the kinematic locus of the 3 { kpc } Arm .