riVerRat
Perhaps you should check sources since I believe there is no rt.300 in the U.S.
From this website,
Page not found – US Highways
we get this table
[b](295)
(US 301) [I] (Fredericksburg, VA) (Lee Hall, VA) (120)
US 301 [II] (Farnhurst, DE) Glasgow, DE Sarasota, FL 1099 (1111)
US 302 Portland, ME Montpelier, VT 171
(US 309) (Waverly, NY) (Philadelphia, PA) (214)
Route Start End Length
US 310 Laurel, MT Greybull, WY 108 (114)
US 311 (Roanoke, VA) Eden, NC Randleman, NC (Aberdeen, NC) 78 (211)
(US 312) (Broadus, MT) (Yellowstone National Park, MT) (234)
(US 313) (Galena, MD) (Mardela Springs, MD) (76)
US 319 Wadley, GA Apalachicola, FL 318
(US 320) (Shoshoni, WY) (Riverton, WY) (26)
US 321 Eaton Crossroad, TN + Hardeeville, SC 526
US 322 Atlantic City, NJ Cleveland, OH 494
(US 330) (Lynwood, IL) (Galt, IL) (161)
(US 331) [I] (Flomaton, AL) (Pensacola, FL) (45)
US 331 [II] Montgomery, AL Santa Rosa Beach, FL + 151 (156)
US 340 Frederick, MD Greenville, VA 156
US 341 (Atlanta, GA) Barnesville, GA Brunswick, GA 226 (257)
US 350 La Junta, CO Trinidad, CO 80 (84)
US 360 Reedville, VA Danville, VA 223 (238)
Route Start End Length
(US 366) [I] (Amarillo, TX) (El Paso, TX *) (437)
(US 366) [II] (Williard, NM) (Albuquerque, NM) (73)
(US 370) (Bowie, TX) (Amarillo, TX) (289)
(US 371) [I] (Bemidji, MN) (Little Falls, MN) (131)
US 371 [II] De Queen, AR Evelyn, LA 214
US 377 Stroud, OK Del Rio, TX * 478
US 378 Conway, SC Washington, GA 234
US 380 Greenville, TX San Antonio, NM 673
(US 383) (Elm Creek, NE) (Oakley, KS) (175)
(US 385) [I] (Raton, NM) (Boerne, TX) (773)
US 385 [II] Pluma, SD Big Bend National Park, TX 1206
US 395 Laurier, WA * Cajon Jct., CA + (San Diego, CA) 1305 (1490)
(US 399) (Bakersfield, CA) (Ventura, CA) (136)
US 400 Joplin, MO + Granada, CO 488
Route Start End[/b]
I do not see a route 300 do you?