What State Lies Between California and Washington?

Oregon. It directly borders California to the south and Washington to the north along its full ~300-mile north-south extent.

Border Details

• California-Oregon: 42nd parallel north (straight line, ~200 mi) — established 1819 Adams-Onís Treaty
• Oregon-Washington: Columbia River (west) + 46th parallel (east) — ~300 mi

Geographic Context

The three states form the contiguous US Pacific Coast tier:

• California (163,696 sq mi) — largest, most populous
• Oregon (98,379 sq mi) — diverse: coast, Cascades, high desert, Willamette Valley
• Washington (71,298 sq mi) — Puget Sound, Cascades, eastern drylands

Major Cross-Border Corridors

• I-5: Continuous San Diego → Seattle → Vancouver, BC
• US-101: Coastal route (mostly)
• Rail: Amtrak Coast Starlight (LA → Seattle)
• Air: PDX (Portland) hub between SFO/LAX and SEA

No other state touches both California and Washington. Nevada borders California only; Idaho borders Washington only.