Mill Creek (Walla Walla River tributary)

Mill Creek
The flood diversion dam on Mill Creek upstream of Walla Walla
Location of the mouth of Mill Creek in Washington
Physical characteristics
SourceBlue Mountains
 • locationColumbia County, Washington
 • coordinates45°59′58″N 117°55′42″W / 45.99944°N 117.92833°W / 45.99944; -117.92833
 • elevation4,800 ft (1,500 m)
MouthWalla Walla River
 • location
Walla Walla County, Washington
 • coordinates
46°02′19″N 118°28′43″W / 46.03861°N 118.47861°W / 46.03861; -118.47861
 • elevation
594 ft (181 m)
Length36.5 mi (58.7 km)
Basin size113.7 mi2 (294 km2)
Discharge 
 • locationAbout 1.5 mi (2.4 km) upstream from Walla Walla
 • average79.9 cu ft/s (2.26 m3/s)
 • minimum0 cu ft/s (0 m3/s)
 • maximum3,070 cu ft/s (87 m3/s)

Mill Creek is a 36.5-mile-long (58.7 km) tributary of the Walla Walla River, flowing through southeast Washington and northeast Oregon in the United States. It drains from the western side of the Blue Mountains into the Walla Walla Valley and flows through the city of Walla Walla, which draws most of its water supply from the creek. The creek is named for the sawmill built in 1845 by Marcus Whitman, one of the first European settlers in the valley.