Map of the former Japanese provinces with Iwaki highlighted
Iwaki (磐城国 Iwaki-no kuni) was an old province in the area that is today Fukushima Prefecture. It was sometimes called Banshū (磐州).
This iteration of Iwaki Province was established in Meiji Era. It was cut out of Mutsu Province and corresponded to the eastern part of modern Fukushima Prefecture on December 17 of 1868 of Japanese calendar, which is January 19, 1869 of Gregorian calendar. Its population in 1872 was 348,608.
Media related to Iwaki Province (1868) at Wikimedia Commons