Question: What forms the western boundary of the county that WAID is licensed to?

Context paragraphs:
McKenzie Mountain Wilderness Area: The McKenzie Mountain Wilderness Area, an Adirondack Park unit of the Forest Preserve, lies in western Essex County in the towns of St. Armand, North Elba and Wilmington.  In general, the Saranac River and Franklin Falls Pond border on the north; the Wilmington-Franklin Falls road, the Whiteface Mountain Memorial Highway and the west branch of the Ausable River form the eastern boundary; the Saranac Lake-Lake Placid Road, NY 86, forms the southern boundary; and the Saranac River forms the western boundary.

Cathays (electoral ward): The Cathays ( ) electoral ward of Cardiff consists of some or all of the following areas: Blackweir, Cardiff city centre, Cathays, Cathays Park and Maindy in the parliamentary constituency of Cardiff Central.  It is bounded by Gabalfa and Birchgrove to the north; Plasnewydd and Adamsdown to the east; Butetown to the south; and Riverside to the west.  The River Taff forms its western boundary to where it meets the South Wales Main Line, the South Wales Main Line forms the southern boundary to where it meets the Valley Lines northbound branch, this railway line then forms the eastern boundary as far as the A48 road.  The Northern boundary follows the A48 as far as Allensbank Road where it follows this road south then turns north again along Whitchurch Road.  It turns west along Crown Way, then south along the A470 until North Road where it bears west, passing just south of the student halls, until it meets the River Taff.  The tallest building in Wales is here and is also part of the Cardiff's CBD.

WAID: WAID (106.5 FM) is a radio station broadcasting an Urban Contemporary format.  Licensed to Clarksdale, Mississippi, USA, the station, also known as "Power 106.5," is currently owned by Radio Cleveland and features programming from ABC Radio .  The station broadcasts the nationally syndicated Tom Joyner Morning Show and Doug Banks show.

25th meridian west from Washington: The 25th meridian of longitude west from Washington is a line of longitude approximately 102.05 degrees west of the Prime Meridian of Greenwich.  In the United States of America, the meridian 25 degrees west of the Washington Meridian defines the eastern boundary of the State of Colorado, the western boundary of the State of Kansas, and the western boundary of the State of Nebraska south of the 41st parallel north.

Holgate, North Yorkshire: Holgate is a suburb and unitary authority ward in the City of York.  It is bounded by the River Ouse from Scarborough Bridge to Ouse Acres on its northern boundary.  Its western boundary is formed by one side of Carr Lane and Ouse Acres to the junction of York Road/Acomb Road, which forms part of the southern boundary.  The remainder of the southern boundary follows Moorgate and Holgate Beck to the East Coast Main Line railway which completes the eastern boundary as far as the River Ouse/Scarborough Bridge.

Pepperbox Wilderness Area: The Pepperbox Wilderness Area, an Adirondack Park unit of the New York Forest Preserve, lies entirely within the town of Webb in Herkimer County.  Stillwater Reservoir and the Beaver River Primitive Area form the southern boundary, while the north bank of the West Branch of the Oswegatchie River generally forms the northern boundary.  The western boundary is the county line, and the eastern boundary is the Raven Lake Road and the Five Ponds Wilderness Area.

Clarksdale, Mississippi: Clarksdale is a city in Coahoma County, Mississippi, and seat of the county.  The western boundary of the county is formed by the Mississippi River.  Located in the Mississippi Delta region, Clarksdale is an agricultural and trading center.  It has been home to many blues musicians.  Clarksdale is named after John Clark, who founded the city in the mid-19th century.

Former Region 5 (Johannesburg): Region 5 was an administrative district in the city of Johannesburg, from 2000 to 2006, covering the greater Roodepoort, Randburg, Olivedale and Northriding areas on the western flank of the City of Johannesburg.  Its long western boundary forming most of the unicity's western boundary.  To the north (Region 1) and east (Regions 2, 3, and 4) it shared boundaries with largely prosperous residential areas.  To the south, it met the northern boundary of Region 6, Doornkop/Soweto.  The region was abolished with a reorganisation of regions in 2006.

Pharaoh Lake Wilderness Area: The Pharaoh Lake Wilderness Area, an Adirondack Park unit of New York's Forest Preserve, straddles the Essex County-Warren County line in the towns of Ticonderoga, Hague, Horicon and Schroon.  The county road along the east shore of Schroon Lake forms the western boundary; to the north, private land and NY 74 form the boundary.  The state land boundary forms most of the remaining perimeter except for a stretch of NY 8 on the south.

Withlacoochee River (Suwannee River): The Withlacoochee River originates in Georgia, northwest of Nashville, Georgia.  It flows south through Berrien County where it joins the New River and forms part of the boundary between Berrien and Cook counties.  It then flows south into Lowndes County, Georgia.  At Troupville, Georgia the Little River joins the Withlacoochee River flows continues to flow south and forms part of the boundary between Lowndes and Brooks counties in Georgia.  The river then flows into Florida for 1.34 miles Florida before returning into Georgia for an additional 2.44 miles.  It then returns to Florida, forming the northeast boundary of Madison County, Florida and the western boundary of Hamilton County, Florida and eventually merges with the Suwannee at Suwannee River State Park west of Live Oak.  The river is 115 mi long.  It is believed to be the source for the name of the central Florida river of the same name.

Supporting paragraphs: WAID Clarksdale, Mississippi
Answer: the Mississippi River