Immediately adjacent to the valleys are the bluffs, forming a narrow belt, usually too much broken for cultivation, but a short distance back the land becomes gently rolling, and is well adapted to farming purposes. The Missouri, one of the great rivers of the continent, forms the western boundary of the county as far up as the mouth of the Big Sioux River. Thence, to the northwest corner, a distance of about five miles, the latter stream marks the western boundary. The principal streams flowing through the interior are Floyd, east and west forks of the Little Sioux, and Maple Rivers. Perry Creek is also a stream of considerable size. All these streams flow through rich and beautiful valleys, and receive many small effluents that completely drain the entire surface. The Little Sioux and Floyd Rivers furnish waterpower for the machinery. There is a deficiency of native timber in this, as in other counties of this part of the State. There are some groves of valuable timber, however, bordering on the Missouri and along the Big and Little Sioux Rivers. The varieties common are cottonwood, hickory, oak, walnut, elm, and maple the first named largely predominating along the Missouri River. It has been found that many kinds of timber may be easily propagated, and when planted on the prairies make a rapid growth.
The geological formation is such as to allow but few exposures of rock in the county, or indeed, in this portion of Iowa. The entire surface is covered by the peculiar formation known by the name of “bluff deposit,” extending to the depth of many feet. The bed of the Missouri River at Sioux City is 340 feet above that of the Mississippi at Dubuque, in the same latitude. There are at Sioux City, and one or two other places, exposures of a sandstone formation of the cretaceous age, with a stratum of soft, chalky limestone overlying it. This is too soft for masonry, but is used for making quicklime. The sandstone is quarried for ordinary building purposes. The same formation appears on Big Sioux River about two miles above the mouth, and extends, with occasional exposures, to the northwest corner of the county. The surface of the “bluff deposit” is used for making brick. The clays in the cretaceous deposit furnish an excellent material for making pottery. Woodbury, however, must rely chiefly on its fertile prairies for its development into a prosperous and wealthy county.
Source: Woodbury County Iowa, History of Western Iowa, 1882