This district encompasses the southwest corner of the state and includes all of Yuma County and the part of La Paz County that does not lie in District 3. The boundary between this district and District 3 on the north generally follows US-60 from the Maricopa County line west to a point east of the town of Quartzsite and the intersection with State Route 95. The district line then dips south to the border of the Yuma Proving Grounds, follows that boundary west approximately 10 miles before jutting north in an irregular line to Milepost 11 on I-10 west of Quartzsite. The line goes north from I-10 to the border of the Colorado River Indian Reservation, following the reservation boundary north (including it in this district) until it meets the Colorado River at a point north of the town of Parker. This district includes the Yuma Naval Air Station, the Yuma Proving Grounds, parts of the Goldwater Air Force Range and several national wildlife refuges.