Well, I stumped everybody this time. In the photo above, soldiers on military motorcycles travel past the Maryland Hotel during the Liberty Loan Parade in 1917.
There was much more to the cross-town parade than motorcycles:
There were Liberty Loan Parades throughout the U.S. during World War I.
Citizens were encouraged to loan money to the government via the purchase of war bonds, which were promoted as a patriotic duty.
Even children, including Boy Scouts, promoted and participated in the program:
There were four issues of Libery Bonds, and more than $21 million was raised nationwide to help fund the war effort for the U.S. and its allies.
After the war, each bond could be redeemed for its purchase price plus interest.
Pasadenans were involved in the war effort from beginning to end.
Here's an excerpt from Ann Scheid's book "Historic Pasadena: An Illustrated History."
The outbreak of World War I in 1914 gave a great boost to Pasadena's tourist trade, as wealthy Easterners could no longer frequent their favorite resorts in Europe. And Pasadenans and visitors alike organized relief efforts, beginning in late 1914 with the founding of a local chapter of the American Red Cross. Dr. James Scherer and Mrs. James A. Garfield were among the founders. The local chapter distinguished itself by being the first to organize and equip a Red Cross Ambulance. The Pasadena chapter sent thousands of surgical dressings, hospital supplies, and refugee garments to Europe and in three years collected almost $200,000 for war relief. Other relief groups in Pasadena added the Belgians, Italians, Syrians, and Armenians.
In drives for Liberty Loans and War Savings Stamps, Pasadenans subscribed over $9 million. Education in food conservation and thrift extended down to the smallest children, who were encourage to perform small household tasks for money; in ten weeks Pasadena schoolchildren earned and saved $5,500 for the war effort. A fabricated ship, "The Good Ship Thrift," built over the body of an automobile, toured the town campaigning for membership and enrolling over 2,100 citizens. Once the United States entered the war, the Navy League (later the Army and Navy League), under the leadership of Mrs. Myron Hunt, set up a knitting program, with 4,000 knitters knitting 61,000 garments in little over a year.
This photo shows the Pasadena chapter of the American Red Cross entry in the 1918 Rose Parade: