This image of the William H. Boyes monorail is from 1911 and can be found in the Library of Congress Prints and Photographs Online Catalog. The Monorail Society has a description of the monorail which appears below.
This test track was built and demonstrated in 1911 in the tideflats of Seattle, Washington. The rails were made of wood and track cost was estimated to be around $3,000 per mile. A bargain! The Seattle Times commented at the time that "the time may come when these wooden monorail lines, like high fences, will go straggling across country, carrying their burden of cars that will develop a speed of about 20 miles per hour." Like so many inventions, lack of financial backing prevented further development.
X-20 Monorail Toy (1962)
Frederick & Nelson Ad (1962)
Closer Than We Think! Monoline Express (1961)
Amphibian Monorail (Popular Science, 1934)
Monorails at Disneyland (1959 and 1960)
Like Earth, Only in Space . . . and with monorails (1989)
600 Miles An Hour (1901)