Question: Which tributary near Meyerstown, West Virginia has two forks approximately 100 mi long each
Context: The Amite River is a tributary of Lake Maurepas in Mississippi and Louisiana in the United States.  It is about 117 mi long.  It starts as two forks in southwestern Mississippi and flows south through Louisiana, passing Greater Baton Rouge, to Lake Maurepas.  The lower 37 mi of the river is navigable.  A portion of the river is diverted via the Petite Amite River and Amite Diversion Canal to the Blind River, which also flows to Lake Maurepas. Myrtle Creek is a short tributary of the South Umpqua River in Douglas County in the U.S. state of Oregon.  Its main stem, formed by the confluence of two forks just south of the city of Myrtle Creek, is only about 1 mi long.  Its only named tributaries are the two forks, North Myrtle Creek and South Myrtle Creek, each of which is much longer than the main stem. Forks of Waters (formerly Strait Creek) is an unincorporated community located in Highland County, Virginia, United States.  Forks of Waters is located approximately 6 mi northeast of Monterey, Virginia at the junction of U.S. Route 220 and Virginia State Route 642.  Forks of Waters is so named due to the convergence of the Strait Creek with the South Branch Potomac River near the community.  After passing through Forks of Waters, the South Branch Potomac River enters West Virginia approximately 1 mi to the northeast. Champoeg Creek is a tributary, roughly 6 mi long, of the Willamette River in the U.S. state of Oregon.  The creek is formed by the confluence of its two forks in the French Prairie region of the Willamette Valley and flows generally northeast to meet the Willamette 45 mi from the river's confluence with the Columbia River.  Its course lies entirely in Marion County. The Yuba River is a tributary of the Feather River in the Sierra Nevada and eastern Sacramento Valley, in the U.S. state of California.  The main stem of the river is about 40 mi long, and its headwaters are split into North, Middle and South Forks.  The Yuba River proper is formed at the confluence of the North and Middle Forks.  Measured to the head of the North Fork, the Yuba River is just over 100 mi long. Shannon Creek is a short tributary to the Baker River in Whatcom County, Washington, near the southwest border of North Cascades National Park.  It rises in two forks a few miles south of Mount Shuksan; the glacier-fed north fork begins at elevation 5016 ft , and the non-glacial south fork begins at 2611 ft .  Roughly halfway through its length, the two forks join and then flow into Baker Lake reservoir, at elevation 725 ft .  Shannon Creek joins the Baker several miles downstream of Sulphide Creek and upstream of Swift Creek, a much larger south-flowing drainage. Short Creek is an unincorporated community in Brooke County, West Virginia, US.  Approximately 1/2 mile from the Ohio River, Short Creek flow from Northern Ohio County into Brooke County.  The creek, Short Creek, has two forks, North and South Fork.  Both forks rise in the very western reaches of Washington County, and very southwestern Allegheny County, in Pennsylvania.  There are several very small settlements along the creek.  There were small family farms and coal mines along the creek. Meyerstown is an unincorporated community near the Shenandoah River in Jefferson County, West Virginia, United States.  Myerstown is a small unincorporated community south of Kabletown, at the intersection of Kabletown Road and Myerstown Road.  It apparently was named for Joseph Myers, a prosperous farmer, who owned several large tracts of land along Kabletown Road. The Shenandoah River is a tributary of the Potomac River, 55.6 mi long with two forks approximately 100 mi long each, in the U.S. states of Virginia and West Virginia.  The principal tributary of the Potomac, the river and its tributaries drain the central and lower Shenandoah Valley and the Page Valley in the Appalachians on the west side of the Blue Ridge Mountains, in northwestern Virginia and the Eastern Panhandle of West Virginia. The Stillaguamish River is a river in northwest Washington in the United States.  It is mainly composed of two forks, the longer North Fork Stillaguamish (45 mi ) and the South Fork Stillaguamish.  The two forks join near Arlington.  From there the Stillaguamish River proper flows for 22 mi to Puget Sound.  The river's watershed drains part of the Cascade Range north of Seattle.
Answer: Shenandoah River