Voted one of the top 45 hikes in the west by Sunset Magazine, the Echo Mountain Trail via the Sam Merrill Trail is definitely worth the hike. This 10-mile trail is of moderate difficulty and allows pooches as long as they are on-leash. Pick up the trail at the Cobb Estate on the corner of Lake Avenue and East Loma Alta Drive in Altadena, California where you can park on the street.
This is a history-filled walk starting with the Cobb Estate, built by Charles Cobb in 1918. After leaving the driveway of the Cobb Estate, you will cross a ravine on a spillway and then start the climb using switchbacks that meander along the edges of the mountain. There is not much shade, so bring a hat and wear some sunscreen. Also, bring lots of water for both you and your little fur baby. The trail is well-maintained and is even shored up by wood where it is steep to make it safer.
Along the trail, you will see quite a few plaques with information marking each spot where you can see remnants of the railway or other historical interests such as some old gears, stone steps to the old Echo House, and the Echo Phone where you can yell out over the valley and hear the echo. The Echo Mountain House is now just a remnant of the old hotel built by Thaddeus Lowe in the 1800s. It was destroyed by fire in the 1900s, but you can see some of the sections of the hotel and the railway that went to the building. Sam Merrill rebuilt the trail here after the hotel was destroyed, and most of the existing trail was washed away.
Besides the historic sites, there are also many areas with beautiful views of the Los Angeles area, especially from the stairs of the Echo House on the summit. You and Fido will probably want to visit again during a different season to see the changes in flora and fauna.