Seattle to Phoenix: No Straight-Line Route Within U.S. Borders

A straight-line (great-circle) path from Seattle, WA (47.6°N, 122.3°W) to Phoenix, AZ (33.4°N, 112.1°W) traverses ~1,100 miles—but most of it lies outside U.S. territory.

The Geographic Problem

The direct line crosses:

1. Pacific Ocean (off Washington/Oregon coast)
2. Northern California (briefly)
3. Pacific Ocean again (off Northern California)
4. Mexico (Baja California peninsula, Gulf of California, Sonora)
5. Re-enters U.S. at Arizona border near Yuma

Practical Driving Routes

• I-5 South → I-8 East: ~1,450 mi, 21 hrs (Sacramento, LA, San Diego, Yuma)
• I-84 East → I-15 South → I-40 East: ~1,400 mi, 20 hrs (Boise, Salt Lake, Flagstaff)
• US-97 South → I-5 South → I-8 East: ~1,350 mi (shorter but slower mountain roads)

Why No Direct Interstate?

The Cascade Range, Sierra Nevada, Mojave Desert, and Colorado River create formidable barriers. I-5 hugs the coast; I-15/I-40 skirt the deserts. No political or economic imperative justified a direct diagonal interstate through low-population, high-construction-cost terrain.

Fly instead: 2.5 hrs nonstop (SEA–PHX), ~30 flights daily.