as a scenic highway by the California Department of Transportation. History La Habra to West Covina connection Although defined to be a continuous route in the California Streets and Highway Code, the segment from Whittier Boulevard in La Habra to West Covina is not officially adopted or signed by Caltrans. This is indicated at the intersection of Whittier Boulevard and Harbor Boulevard, where an "END 39" sign appears. Prior to the present before reaching Harbor Boulevard, SR 39 continued north from Whittier Boulevard along Hacienda Road to the Los Angeles/Orange County line then north on Hacienda Boulevard and Glendora Avenue to US 60, 70, and 99 (Garvey Avenue, now Interstate 10) in West Covina. It then continued east with US 60, 70, and 99 to Azusa Avenue where it turned north to follow the present alignment as described beginning in the fourth paragraph of the preceding section. The Hacienda Glendora segment can still be seen as Route 39 on some maps. Prior to 1991, Harbor Boulevard became Fullerton Road northbound from the Los Angeles/Orange County Line, through the Puente Hills as a one-lane winding road into Rowland Heights. However, due to complaints of nearby residents due to the increased volume of traffic, a straighter, wider stub was built slightly to the east, and was named Harbor Boulevard. This route is under consideration to become part of SR 39 to complete the gap. The new Harbor Boulevard was opened to the public early in 1992, and is now the primary corridor between Orange County and Rowland Heights, although the original winding Fullerton Road segment still exists as a strictly residential street. The definition of Route 39 in the California Streets and Highway Code was thus changed accordingly, and the traversable route to fill the Route 39 gap would be via Harbor Boulevard north, Fullerton Road north, and then Colima Road west to Azusa Avenue in Hacienda Heights. Route 39 would then continue north on Azusa Avenue through the City of Industry to Interstate 10 in West Covina. This segment however has yet to be officially designated by Caltrans. Closed northern segment to Islip Saddle The northernmost stretch of SR 39, from Snow Springs north of Azusa to SR 2 at Islip Saddle, has been closed to public vehicle traffic since 1978 due to a massive mud and rockslide. While the road is passable to emergency vehicles for the entire closed length,