|Slogan: "A Good Road from Plymouth Rock to Puget Sound"|
|Length:||3,719 mi (5,985 km)
According to the 1920 Yellowstone Trail Route Guide.
|History:||The Yellowstone Trail was established on 23 May 1912. The Yellowstone Trail Association was incorporated in 1918, and ceased in 1930.|
|West end:||Seattle, Washington|
|East end:||Plymouth, Massachusetts|
The Yellowstone Trail was the first transcontinental automobile highway through the upper tier of states in the United States, established on 23 May 1912. It was an Auto Trail that ran from the Atlantic Ocean in Plymouth, Massachusetts, through Montana to Yellowstone National Park in Wyoming, to the Pacific Ocean in Seattle, Washington.
The Yellowstone Trail was conceived by Joseph William Parmley of Ipswich, South Dakota. In April 1912 the first step he and his local influential colleagues wanted was a 25 miles (40 km) long good road from Ipswich over to Aberdeen, also in South Dakota. By May, the intent had expanded to get a transcontinental route built, including to the popular tourist destination to the west, Yellowstone National Park.
The automobile was just becoming popular, but there were few good all weather roads, no useful long distance roads, and no government marked routes. The federal government had not been interested in building roads in the nineteenth century, except for the National Pike from Washington D.C. to the Mississippi River. Many states had constitutions that forbade “internal improvements” as unconstitutional. The Yellowstone Trail developed in parallel with the nationwide effort for internal improvements, which included building and improving roads. Only the Yellowstone Trail, the Lincoln Highway, and the National Old Trails Road were transcontinental in length and notability, out of the 250 named Auto Trails of the era. 
In June 1915, a timed relay race from Chicago to Seattle was held on the Trail. The 2,445 miles (3,935 km) route was won with a best time of 97 hours. There were no deaths in the race, but accidents did happen. One was in Eau Claire, Wisconsin, when a George Murphy was 'speeding recklessly' at 26 mph (42 km/h) in his Mitchell 6, en route to Menomonie from Chippewa Falls. He skidded when coming downhill around a corner, and crashed into a tree. He survived, and finished his relay segment to Menomonie in a backup car.
Yellowstone Trail Association
The Yellowstone Trail Association incorporated in January 1918, with the head office in Minneapolis. It formed state chapters and smaller town chapters to oversee routing in the Midwest and West. Local "routing committee men" went out into their counties to find the best roads available, and then talk the counties' governments into spending tax dollars on that route. They then persuaded small towns on the Trail to join the organization, and pay a small fee to be included in the route's publicity materials.
The Yellowstone Trail Association also served travelers' information needs, much as the AAA—American Automobile Association had been doing for drivers in the U.S. The Trail Association published maps and brochures, and established information bureaus in popular hotels and in tents along busy sections of the Trail, to hand out these materials. Travelers could telephone the Trail Association before planning a trip, to see which roads were passable. The information bureaus also provided local information, much as Convention and Visitors Bureaus do in the present day.
After the Great Depression began in 1929, the Yellowstone Trail and other named Auto Trails lost their allure and affordability. The main Yellowstone Trail Association office was closed on 15 March 1930. Its replacement organization, the Yellowstone Highway Association, operated marginally until around 1939.
- Eastern United States
In the Eastern United States, the Yellowstone Trail Association exerted little influence on the road's routes. Instead it functioning primarily as a travel information bureau to entice tourists westward along the Trail.
A few streets and roads retain the Yellowstone Trail name in the East, and some former sections remain as unimproved roads. The Yellowstone Trail garages and route signs are gone. Former sections, some with signage, still exist in travelable condition in Wisconsin, Montana, and Washington. 
- Good Roads Movement
- National Old Trails Road (1912)
- Lincoln Highway (1913) — first completed transcontinental Auto Trail.
- Index: Auto trails of the United States
- Meeks, Harold A. (2000). On the Road to Yellowstone. Missoula, Montana: Pictorial Histories Publishing Company. ISBN 1-57510-079-7.
- The Yellowstone Trail Assoc., History
- Yellowstone Trail.org; "The Yellowstone Trail Association, Then and Now"; accessed 11.25.2012
- "Internal Improvements Acts". Answers.com. Retrieved 2007-06-08.
- Ridge, Alice A. and Ridge, John William. Introducing the Yellowstone Trail: a Good Road from Plymouth Rock to Puget Sound, 1912-1930. Altoona, Wis.: Yellowstone Trail Publishers, 2000. ISBN 978-0-97028-320-7
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