US malaria information from the CDC

[Nadja Adolf]

http://www.cdc.gov/ncidod/EID/vol2no1/zuckerei.htm

This website contains maps showing areas where malaria was believed
endemic in 1882 and 1912.
The Willamette Valley is prominent among them.

They also list a number of Anopholes mosquitoes, and note that there are
mosquitoes capable
of transmitting malaria in all the "Lower 48."

They believe malaria was brought from Europe and Africa.