- Island Number 18 (historical)
- Iceberg Island
- Ika Island
- Illahee
- Illia
- Ilwaco
- Image
- Impach
- Inchelium
- Independence
- Index
- Indian Beach
- Indian Island
- Indian Island
- Indian Island
- Indian Island
- Indian Village
- Indian Village Mobile Home Park
- Indianola
- Inglesea
- Inglewood
- Inglewood
- Inglewood Estates Mobile Home Park
- Inglewood-Finn Hill
- Innis Arden
- Intercity
- Interlake Island
- Interlaken
- Ione
- Iowa Rock