GRUNDY, a new county in the N. E. central part of Iowa, has an area of about 500 square miles. It is drained by Black Hawk creek, an affluent of the Cedar river. This county is not included in the census of 1850, and the population is small. County seat not located. (Baldwin's New and Complete Gazetteer of the United States..., 1854)
GRUNDY COUNTY Is in the fourth tier of counties from the northern boundary line, and the fifth west of the Mississippi river. It is bounded on the north by Butler county, on the east by Black Hawk, on the south by Tama and Marshall, and on the west by Hardin.
It is watered principally by Beaver and Black Hawk creeks, which, flowing in an easterly direction, empty into the Cedar river.
The county is principally high rolling prairie, with a limited supply of timber, and on this account has been somewhat tardy in its settlement, although the soil is as productive as in any part of the State. It was organized in 1856. The DuBuque & Sioux City Railroad passes through the northern portion of the county. (Hair's Iowa State Gazetteer..., 1865)