It’s a nice short trail, and I don’t think many people know about it.

I started on a very warm day, at the parking lot on Glenwood Rd. in Rutland. This trail matches the description perfectly! Beautiful, well-shaded ride and that is pretty continuous. I learned Rutland is the higher point of the ride, so all my work was on the way back from Oakham. But, it was very manageable and well worth the 16+ miles roundtrip.

We bicycled a sort of loop, from Mosely Woods parking lot, along Merrimac River, crossing to Salisbury and then returning via I-95 bridge bike path. The latter was our true goal, as this was a mighty project! From the start and throughout, we had some head-scratching moments trying to find our way on the network of rail-trails and roads. I'm not sure if it's the fault/responsibility of the municipalities, the DOTs, or the trail organizations, but there are few, if any, signs indicating bikeways. This struck us as odd because in many other areas throughout Essex County in Massachusetts, and in parts of NH and ME, we have seen copious signs for the East Coast Greenway in remote countryside locations.
Before I say more on that, we enjoyed the gravel-paved Marsh Trail and Ghost Trail. The latter was shaded and welcome on a very hot summer day. The mile or so of asphalt-paved trail that parallels I-95 and crosses the Merrimac is great for getting from A to B, but it's open and not especially pleasant except for the river views, which can be enjoyed from two bump-outs on the bridge and include historic interpretation signs. (A note: if you are nervous crossing major bridge structures on bicycle, this is a good crossing. I have minor such fears, but felt completely comfortable.)
Back to signs. There are signs. But I don't think they are always where they should be, nor say what they should say. More than once, we came to intersections of various kinds and it was unclear where each option would take us. In some places there are posts with trail names and mileage., but few signs to provide context. Within long stretches of the bike paths there were posts indicating mileage (for what reason, I have no idea). Coming from the Ghost Trail there was no explicit sign to point the way to the I-95 crossing. And in Newburyport, we did not see any signs pointing the way to the trail, crossing via the Route 1 bridge. Coming off the I-95 crossing into Newburyport, we had to intuit the way back to Mosely Woods on a neighborhood road.
My suggestion is that if you are solo or with a partner, have fun and explore, and if you have to do a bit of back-tracking, no big deal. If you have kids, it might be better to thoroughly plot your route, as you don't want to be fumbling on roads with cars with kids or a larger group. That said, it would be a nice adventure to cross by two different bridges and experience a variety of trail types and scenery that runs the gamut from marsh, woods, industrial (including a massive solar array), neighborhood, etc. It is almost all flat, and eminently do-able for people of various fitness levels and bike types.
A note: the Route 1 bridge does not have a bike lane, so you must walk your bike across on a sidewalk, and will likely encounter others either on bike or foot in either direction.

Nearly perfectly flat - good compact ground - three nice bridges - very little other traffic.
We had two kids, 8 and 11, with medium bike skills - easy going here so was all fun and no hassle. We started in the middle (parking area) and went to each end and back. Total 6 miles, took 1 hr due to stops to view wildlife.
Only drawback: we wanted more miles !!

My son and I love riding this on our dirt bikes. Wide and easy to ride, perfect place for a new rider to get comfortable. Plenty of other people on bicycles, hikers, ATVs and dirt bikes on the trail, everyone was friendly and courteous to give each other room. It’s nice having a place like this to spend time with my son.

Beginning at the eastern point in Northampton, this is not well signposted. It connects with the western end of the Norwottuck trail heading west by turning right (turning left goes to the Manhan trail) at the T junction once you have gone through a tunnel having crossed the Connecticut River and crossed a couple of roads. It takes you to Florence / Leeds including the Look Memorial Park in Leeds. Heading west, having turned right onto this trail from the Norwottuck trail it goes behind a commercial building and seems to stop. At this point you come out between these buildings facing a road. Cross this road at the traffic lights and go through the Stop and Shop parking lot to the left of the supermarket building. There is an official gap in the fence where you can join the rail trail. It is not marked. Follow the trail to the right. It is a little bumpy with roots to start with but is a nice scenic paved trail.

An excellent paved trail, with many beautiful places to stop and take in, take a break for lunch, or refreshments! A couple bike shops along the way, just in case, or if you need something. Veer off at Mass Ave to go thru Harvard and Cambridge, lots to see & do!

This is a GREAT trail for biking. Goes all the way to Pope John Paul Park in Dorchester.

This is a lovely oath path but it’s pretty bumpy, not good for road bikes