As stated, the Cowlitz Portage was the termination point of river travel from the Columbia, and the embarkation stage for the overland route to Puget Sound. The farm was established on Cowlitz Prairie, one of many prairies alternating with forests, located between the landing and Fort Nisqually to the north. The prairie was about a mile from the landing. Its size varied, according to who did the estimating: William Tolmie thought it was about four miles long and one mile wide; Duflot de Mofrás thought it was six by two miles, James Douglas said the plain "...contains a surface of about 3000 acres of clear land."  The site, Douglas said in 1839, had the disadvantage of "...being separated from the River by a steep, rugged hill impracticable in its present state, to wheeled carriages: and the excavation of a convenient road, will be an enterprise attended with great labour and expense."  Lieutenant Charles Wilkes, who arrived overland from the north in 1841 noted the farm was located on "an extensive prairie on the banks of that river [the Cowlitz]." He later reported:

I was told that the stock on this farm do not thrive so well as elsewhere: there are no low prairie grounds on that side of the river in the vicinity, and it is too far for them to resort to the Kamass plains, a fine grazing country a few miles distant, where the wolves would make sad depredations with the increase, if not well watched...The hilly portion of the country, although the soil in many parts is very good, is so heavily timbered as to make it in the present state of the country valueless; this is also the case with many fine portions of level grounds; but there are large tracts of fine prairie suitable for cultivation and ready for the plough. 

Eugene Duflot de Mofrás, at Fort Vancouver the same year as Wilkes, described the Cowlitz River route:

Fort Cowlitz is situated on the river of the same name and rises on a plain 6 miles long and 2 miles wide. This river, on whose banks beds of coal and lignite are exposed, rises, as does the Nisqually, on the slopes of Mt. Rainier and empties into the right bank of the Columbia River, a few leagues above its mouth. Its channel, navigable only by barges, is extremely tortuous, being filled with fallen trees, rocks and rapids that make its passage hazardous. At narrow points its banks are steep and great masses of granite formation thickly covered with forests tend to give this country a wild and somber aspect Occasionally, where the country is fairly level, plains covered with rich pasturage are visible. The number of hectares placed under cultivation through the Company's efforts is approximately 100. 

By the spring of 1840, some houses had been built, and by the spring of 1841, when Charles Wilkes visited the site, a dairy was in operation, and both a gristmill and sawmill were under construction.  In 1845-46 a dwelling, granaries and outbuildings were erected at the mouth of the Cowlitz River to store the farm's produce until Company vessels could pick it up.  The inventory of structures in 1846-47 listed a fifty by thirty foot dwelling house; a forty by one hundred foot store and two forty by thirty foot stores, two granaries and the sawmill "& improvements attached, incomplete." In addition, there were a number of outbuildings listed, including thirteen 105 by twenty foot barns, a "close bam," eighty by twenty-five feet, two piggeries, two stables, and six "men's houses."

Two maps of "Cowelitz" Farm as cultivated in 1844-45, and 1845 and Spring 1846 shows the farm's organization to be compact, much more similar in nature to Nisqually's organization than to Fort Vancouver's, obviously due to the acreage available on its large plain. It was organized in a series of abutting rectangular and square fenced fields ranging in size from around nine to 105 acres. Some of the larger fields had the 105 by twenty foot barns, or grain sheds located within them. In the approximate center of the farm was a long rectangular enclosure in which were located two grain sheds and two barns in a line running southeast. Southeast of these were a cluster of buildings, which are not identified on the map, but must have been the dwelling house and possibly the store. Southeast of these, on the banks of a stream, were pigs styes--in 1846 the farm housed around three hundred hogs, excluding the young ones--and a stable, and three houses. Beyond the fenced enclosures, to the east on the plain, were several dwellings. The fields were numbered, and a comparison between the maps shows that crops were rotated within the different fields, although the fields ranging along the southeasterly edge of the farm appear to have been laid down permanently in timothy and clover. An employee later said the Company had "a comfortable, comodious dwelling house; a large two-story granary, with barns and sheds, conveniently distributed at various points over the farm." The lack of a road noted by Douglas in 1839, had been remedied by 1845: "They had a wagon road to the bank of the Cowlitz River, made at considerable cost," The sawmill was located near the Cowlitz River, and sheep--by 1846 about one thousand--were pastured on lands to the north of the farm; horses were pastured on the opposite bank of the Cowlitz.