Old Main Line (HoCo Thru Trail)

Old Main Line (HoCo Thru Trail) is a short, easy “green” multi-use rail-trail segment inside Patapsco Valley State Park in Howard County, Maryland. Expect a mostly flat walk along the Patapsco River corridor, using a historical rail-bed alignment rather than a winding footpath.

The route runs primarily as dirt double-track/rail-trail tread. It’s designed for hiking and also accommodates other non-motor uses (including mountain biking) while remaining open to horses, and dogs must be leashed.

On the ground, the character is rail-trail easy grades with minor elevation change (about 35 ft gain and 70 ft descent reported for the segment). For walkers, the work is mostly steady pacing rather than steep climbing.

Along this section you’re following the old B&O Railroad alignment near the river, with historical remnants like stone culverts and park ruins appearing along the corridor.

Access is typically through Patapsco Valley State Park’s Daniels Area (Daniels Road Trailhead at 2090 Daniels Rd, Ellicott City). Parking there is very limited, so plan to arrive early if you’re starting from Daniels.

If you want to link this segment into a longer day, it’s part of the wider Patapsco Valley “thru-trail” system managed through the Patapsco trail stewardship network.

More information: Walking on History Along the Old Main Line Trail, About - Friends of Patapsco Valley State Park, Patapsco Valley State Park - Daniels Road Trailhead