It curves northeast again at a plot of land that was originally intended to be the southern terminus of CR 103 (Cedar Swamp Road), then enters a series of Suffolk County Government buildings, where it finally terminates at an at-grade intersection at NY 24 and CR 94 in Riverside.

The route begins at Sound Avenue in Wading River, with Hulse Landing Road continuing south from the intersection.

Although there was signage at the southern terminus of Hulse Landing road at NY 25A, the portion of CR 54 between Sound Avenue and 25A has been decommissioned.

The road formerly began at NY 25A near land formerly owned by the Calverton Naval Weapons Industrial Reserve Plant.

Between NY 25A and Sound Avenue the formerly proposed Nugent Drive Extension was supposed to cross over CR 54 at an interchange.

As the name implies, the road originally went from Manorville to Eastport, and was acquired by the Suffolk County Department of Public Works in 1935.

[10] Construction of the vast and complex exit 61 interchange forced the realignment of CR 55, as well as Head of the Neck Road.

After the intersection of River Road, a westbound on-ramp to Sunrise Highway, which was originally built with two different access points.

It skirts along the south end of the runway for Brookhaven Airport west of Winters Drive, and goes as far east as Barnes Road in Moriches.

Eastbound and westbound carriageways are separated by two different underpasses beneath the interchange with NY 27 (Sunrise Highway), both of which briefly join the service roads.

County Route 58, locally known as Old Country Road, serves as a northern bypass of the section of NY 25 that runs through the downtown area of Riverhead.

The portion of the road between the outlet center and the traffic circle at CR 73 has been the site of the most active retail development, spread over several decades.

As such, the road's width and treatment vary because the task of widening largely fell to each individual developer of the new strip malls.

The western interchange indicates a potential proposal to widen the road to a possible four-lane divided highway that was never built.

County Route 61 is unsigned Waverly Avenue, a mainly two-lane road that runs north and south along the Islip–Brookhaven town line until the town line makes a sharp left along the Greenport Branch of the Long Island Rail Road.

The last intersection within range of the town of Islip is for Furrow Roads (eastern terminus of CR 90) and Barretts Avenue, both of which were once intended to be integrated into the Central Suffolk Highway.

However, until CR 97 (Nicolls Road) was extended to the Long Island Expressway, it served as one of the eastbound destinations for exit 62.

After passing by some marinas and shore front homes, CR 62 seems to terminate at a T-intersection, but in reality makes a right turn at that intersection onto Sunset Avenue.

The road then runs through the Sans Soucci Lakes County Park, with a driveway to the NRHP-listed John Ellis Roosevelt Estate on the north side.

At the intersection with the two-lane divided Edgewater Avenue, CR 65 takes a northeasterly turn and serves as the southern border of Bayport Commons Park.

After this fiasco, the road passes Bergen Avenue and makes a slight curve to the northeast, only to curve east again and cross the Corey's Creek Bridge, where one can find sites such as the Blue Point Marina, Corey's Creek Park, and a local roadside luncheonette.

[10] The only other major intersection between the two termini of CR 66 is a segment of DeForest Road which begins as the off-ramp of exit 42N of the Northern State Parkway.

[30] CR 68 begins as Main Street at NY 25A near the Stony Brook Museum and Carriage House, as a north–south road.

It begins at a segment of NY 25A that briefly runs north and south within Stony Brook before making a sharp right turn towards Setauket, Port Jefferson and points east.

A west-to-northbound ramp exists on the northeast corner of the intersection, When CR 68 runs through the Stony Brook village center, it turns into an east–west road.

The rest of CR 68 is surrounded by historic houses, although it also includes the North Shore Montessori School and a local Methodist Church and Cemetery.

The former connecting north-to-eastbound ramp which was used by eastbound NY 25A can still be seen on the southeast corner of North Country Road and Ridgeway Avenue.

[35] It terminated at NY 27A (now CR 80), but Atlantic Avenue continues northbound into Pine Street, the former location of East Moriches Station.

County Route 73 is Roanoke Avenue from downtown Riverhead north towards the farms along the Long Island Sound.

Roanoke Avenue in Downtown Riverhead was originally part of CR 43 between NY 25 (Main Street) and Northville Turnpike.