Seventy-nine congressional districts sit entirely inside one county, never crossing its line. Ten of those seventy-nine are inside Los Angeles County: CA-27, CA-28, CA-29, CA-31, CA-32, CA-34, CA-37, CA-38, CA-43 and CA-44.
That is one county holding more House seats than 42 states do.
Where the rest of them are
| County | Districts wholly inside | Which |
|---|---|---|
| Los Angeles, CA | 10 | CA-27, 28, 29, 31, 32, 34, 37, 38, 43, 44 |
| Maricopa, AZ | 5 | AZ-1, 3, 4, 5, 8 |
| San Diego, CA | 4 | CA-49, 50, 51, 52 |
| Harris, TX | 4 | TX-7, 9, 18, 38 |
| Cook, IL | 4 | IL-5, 7, 8, 9 |
| Kings, NY | 3 | NY-7, 8, 10 |
Add Orange and Riverside and San Bernardino and the pattern is the whole southern half of California. Of the state's 52 seats, 21 never leave the county they start in.
The size range inside those ten
The ten Los Angeles districts are not uniform. CA-34, drawn around downtown and Koreatown, is 129 square kilometres. CA-27, which runs north into the Santa Clarita Valley and the high desert edge of the county, is 3,973. Same county, same delegation, thirty-one times the ground.
This is the practical reason a county-level election map misleads in Los Angeles and works fine in Nebraska. Colour Los Angeles County one shade and you have flattened ten separate representatives into a single block. Colour Nebraska's counties and you have resolved its 3rd district into 79 pieces.
What it does to a ballot lookup
If you look up your ballot from a Los Angeles address, the county tells you almost nothing about which House race you are in. Ten of them are live inside that one boundary and the line between two of them can run down the middle of a street. This is why the address lookup on this site resolves to a district through the Census geocoder rather than stopping at the county, and why the county name alone is never enough south of the Tehachapis.