Based on a report we read here, my girlfriend and I put in with our inflatable kayaks by Lord Stirling park near the intersection of Carlton Rd. and Lord Stirling/Whitebridge Rd.
Took the river all the way to Passaic River Park in Berkeley Heights. River was very swollen from recent rains and a lot of shoreline areas were flooded. Most fun part was Millington Gorge section that occurred in first 3 miles/1 hour of trip. It had some light rapids that made it interesting.
Many down trees along route. Had to portage two sections to get around large trees. Several other sections were made more complicated due to the trees but we made it through. Took about 5.5 hours to complete trip.
These are directly stolen from the poster of the Passaic River-Millington Gorge entry for the put-in:
"From Chatham, take Fairmount avenue south. Right hand turn on Meyersville road. follow to Meyersville, first right in town is New Vernon Road. Follow about a mile, go left on White bridge road another mile to bridge over the Passaic. Cross bridge and fisherman's access parking lot is on right side. Allows good access to river."
Parked in Passaic River Park parking lot in Berkeley Heights for take-out. About a 200 yard walk along soccer field to access river.