State Route 604 currently[update] exists in two discontinuous sections. The first is a 0.119-mile (0.192 km) section of Las Vegas Boulevard at the intersection of Tropicana Avenue.
The second is the 13.288-mile (21.385 km) section of Las Vegas Boulevard from Tonopah Avenue in North Las Vegas. From there, SR 604 intersects at Lake Mead Boulevard SR 147 as it curves east to a northeastern direction from there on. SR 604 eventually enters the unincorporated town of Sunrise Manor where it has intersections at Cheyenne Avenue (SR 574), Lamb Boulevard (SR 610) and Nellis Boulevard (SR 612). After that, SR 604 then enters the Nellis Air Force Base where it intersects at Craig Road (SR 573) and the main entrance of Nellis AFB. The highway then continues northeast as SR 604 passes the Las Vegas Motor Speedway and later re-enters the city of North Las Vegas where there isn't any development around the highway. The highway leaves the city of North Las Vegas shortly after just before SR 604 ends at Interstate 15 at exit 58 near Apex. The I-15 frontage road stretching northeast 11.823 miles (19.027 km) from Apex to a point between Garnet and Crystal is also state maintained as FRCL07, and was mileposted as SR 604.
State Route 604 was created in the 1970s from what had been State Route 6 between Jean, where it intersected with State Route 161, and a point north of Las Vegas. However, it has been truncated over time, as segments were given to the city of Las Vegas and Clark County to maintain. Most recently, the portion between Jean, Nevada and Russell Road was given to Clark County. From the mid-1980s to 2005 this highway was used as the course for the start and a sigifigant portion of the Las Vegas Marathon.