1909 Garden Home Train Depot (view from the east)
Courtesy Colin Lamb.
The Garden Home station was seven miles from downtown Portland. The track to the left goes to Salem, the track to the right goes to twenty one miles to Forest Grove. Oregon Electric service from Portland to Salem began service in January, 1908, and freight traffic in July, 1908. Passenger service to Forest Grove began in October, 1908.
GardenHomeHistory.com 
To be completely accurate: service to Hillsboro along the branch began on October 29, 1908. The first scheduled service to Forest Grove was on December 25, 1908.
Thank you for the clarification/correction!