The route begins in downtown West Chester and heads east out of the borough as a one-way pair of streets.

At this point, both directions of the route join and head east along four-lane divided West Chester Pike, passing through residential areas in the community of Chatwood.

The road curves east-southeast at the Strasburg Road intersection and crosses into East Goshen Township, where it continues past suburban neighborhoods and commercial establishments, crossing the East Branch Chester Creek and passing through the community of Goshen.

The road heads east through wooded areas with residential subdivisions as it continues into Willistown Township.

The route intersects the eastern terminus of PA 926 and curves east-northeast through a mix of fields and woodland with some homes, crossing the Ridley Creek before coming to a junction with Delchester Road.

[3][4] PA 3 enters Edgmont Township in Delaware County as it passes to the north of Ridley Creek State Park.

Following the PA 252 intersection, the route continues east through a mix of suburban residential and commercial areas.

PA 3 has an intersection with Manoa Road as it passes to the north of the Llanerch Country Club, continuing through suburban development.

Farther east, the route crosses Naylors Run and heads into the community of Llanerch, where it intersects Darby Road a short distance before coming to a junction with US 1.

After crossing US 1, PA 3 enters Upper Darby Township and continues past suburban businesses and homes.

The route becomes undivided again and runs past more commercial development, forming the border between the borough of Millbourne to the north and Upper Darby Township to the south.

PA 3 heads past some homes before turning into a divided highway at the eastern edge of Millbourne as SEPTA's Market–Frankford Line rises to pass over the road.

PA 3 follows Chestnut and Walnut street east through residential areas of West Philadelphia, passing several blocks of rowhouses with some businesses.

East of US 13, westbound PA 3 follows on Market Street, a three-lane road with a center left-turn lane.

The route passes several multistory commercial buildings as it runs through the northern part of the Drexel University campus.

The eastbound direction passes to the south of the train station and north of the city's former main Post Office facility as a four-lane undivided street.

Following the construction of 69th Street Terminal in Upper Darby in 1907, the route of the West Chester Pike saw increasing suburban development.

[6] The West Chester Pike was designated as Legislative Route 133 when the Sproul Road Bill was passed in 1911.

[7] In 1927, the West Chester Pike and Market Street in Philadelphia were designated as part of PA 5, which ran along the Lakes-to-Sea Highway.

The viaduct provided a physical and social barrier between areas north and south of Market Street that came to be known as the "Chinese Wall."

However, the Great Depression put these plans on hold and Broad Street Station and the "Chinese Wall" would continue to be used until 1952.

As part of constructing the boulevard, a new bridge was built over the Schuylkill River leading to 30th Street Station.

[14] In 1954, regular trolley service between Philadelphia and West Chester ended as plans were made to widen PA 3.