The upper section, through Washington Rock State Park in Green Brook and on into Watchung, may not be maintained by Somerset County. There is an END 529 assembly at the intersection of Washington Avenue and Rock Road, and there is evidence of municipal maintenance (such as non-standard speed limit signs) between there and Mountain Boulevard (SR 527). The NJDOT straight-line diagram for the highway indicates that the entire road is county-maintained, however.
| Mile | Street Name | Feature | ||
| 10.57 | Northern terminus of , Watchung Boro, Somerset Co |
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| 10.57 | Washington Rock Rd |  Mountain Blvd |
Mountain Blvd |
|
| 9.94 | Rock Rd East | Watchung Boro, Somerset Co Green Brook Twp, Somerset Co |
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| 8.58 | Washington Ave |  |
 |
|
| 8.41 | Washington Ave |  Green Brook Rd |
|
Green Brook Rd |
| 8.12 | Washington Ave | Green Brook Twp, Somerset Co Dunellen Boro, Middlesex Co |
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| 7.53 | Washington Ave |  North Ave |
|
North Ave |
| 7.48 | Washington Ave | Jersey Central Railroad | overpass | Jersey Central Railroad |
| 7.43 | Washington Ave |  New Market Rd |
|
South Ave |
| 7.06 | Washington Ave |  Walnut St |
|
Walnut St |
| 6.95 | Washington Ave | Dunellen Boro, Middlesex Co Piscataway Twp, Middlesex Co |
||
| 6.71 | Washington Ave |  Vail Ave |
|
7 St |
| 6.43 | Washington Ave | Lehigh Valley Railroad | bridge | Lehigh Valley Railroad |
| 6.39 | Washington Ave | Bound Brook | bridge | Bound Brook |
| 6.35 | Washington Ave | Lakeview Ave | |
Lakeview Ave |
| 5.90 | Washington Ave | Evans Ave | |
|
| 5.68 | Washington Ave | Carlton Ave | |
Carlton Ave |
| 5.31 | Washington Ave | Stelton Rd |
|
|
| 5.26 | Stelton Rd | Reading Railroad | overpass | Reading Railroad |
| 5.16 | Stelton Rd | Washington Ave |
|
Washington Ave |
| 4.81 | Stelton Rd | |
Shopping center entrance | |
| 4.72 | Stelton Rd | Piscataway Twp, Middlesex Co South Plainfield Boro, Middlesex Co |
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| 4.72 | Stelton Rd | New Brunswick Ave | |
New Brunswick Ave |
| 4.59 | Stelton Rd | |
Hamilton Blvd |
|
| 4.53 | Stelton Rd | |
Ramp to/from  north |
|
| 4.43 | Stelton Rd | |
overpass | |
| 4.40 | Stelton Rd | Ramp to/from south |
|
|
| 4.17 | Stelton Rd | Centennial Ave | |
Hadley Rd |
| 3.88 | Stelton Rd | |
Shopping center entrance | |
| 3.77 | Stelton Rd |  Metlars Ln |
|
|
| 3.59 | Stelton Rd | South Plainfield Boro, Middlesex Co Piscataway Twp, Middlesex Co |
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| 3.59 | Stelton Rd | |
New Durham Rd |
|
| 3.24 | Stelton Rd | Haines Ave | |
Haines Ave |
| 2.89 | Stelton Rd | School St | |
|
| 2.58 | Stelton Rd | Ethel Rd | |
Ethel Rd |
| 2.29 | |
Piscataway Twp, Middlesex Co Edison Twp, Middlesex Co |
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| 1.91 | Plainfield Ave | |
Brunswick Ave | |
| 1.68 | Plainfield Ave | Kilmer Rd | |
|
| 1.52 | Plainfield Ave | Pennsylvania Railroad | underpass | Pennsylvania Railroad |
| 1.44 | Plainfield Ave | Central Ave | |
Central Ave |
| 1.01 | Plainfield Ave |  Lincoln Hwy |
|
Lincoln Hwy |
| 0.38 | Plainfield Ave | Jeferson Blvd | |
Shopping center entrance |
| 0.25 | Plainfield Ave |  |
|
|
| 0.00 | Plainfield Ave |  Woodbridge Ave |
|
Woodbridge Ave |
| 0.00 | Southern terminus of , Edison Twp, Middlesex Co |
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