Most of the hundreds of trading posts in Saskatchewan resulted from two periods of intense competition: from 1774 to 1821, and again from the 1880s to the 1920s. Over 350 posts are known, but from the latter period only the Hudson's Bay Company (HBC) posts have been documented. The posts varied greatly, ranging from a large, stockaded multi-building complex to a simple cabin used for only one winter, to an Aboriginal family dwelling in a small, isolated bush community. After the mid-1800s, major posts included an HBC trader, one or more competing traders, and a mission. In the north, these complexes formed the core for Aboriginal settlements, which began developing in the late 1800s. Since the traders depended on water transport, posts were built along rivers and lakes, often on traditional Aboriginal gathering grounds.
Typically, the traders arrived from the east with new stocks of goods in late fall. Aboriginal families had already gathered in expectation of their arrival, and after obtaining their supplies on credit quickly left for their wintering grounds. They seldom returned until spring, when they brought their winter furs, paid off their debts, and traded for the remaining merchandise. Immediately after break-up, the traders left with their cargoes of furs. During the summer, posts were abandoned or were maintained by only several men. Then, in the fall, the cycle repeated itself. People seldom came to the posts to trade during the winter. Instead, they sent word for traders to come and fetch their furs, or employees were sent out on short trips with a small stock of goods, traveling from one wintering camp to another. After missionaries arrived in the 1850s, people began to come to the mission for Christmas and Easter, and traded at the nearby posts. By the late 1800s, Aboriginal men were often subcontracted to take goods to their wintering cabins, where they would trade with their neighbours. Others were hired as seasonal freighters. Consequently, by 1900 most posts had only two or three employees-unlike earlier times when they might have over 40 men.
In the south, much of the trade focused on obtaining bison provisions from large camps of Assiniboine or Cree who spent most of the year on, and at the edge of, the northern plains. Several times a year, large groups would arrive at the post bringing hundreds of pounds of pemmican and bladders of fat. Increasingly, Métis from Red River participated in this trade, traveling out onto the plains on annual hunts. As the bison retreated west after the mid-1800s, the Métis followed, often with their own itinerant traders, moving into the Wood Mountain area in the south and to Moose Woods, south of present-day Saskatoon. Consequently, small temporary posts began to be established well out on the plains.
Following the merging of the NWC and HBC in 1821, Governor George Simpson imposed cost-cutting methods by closing many posts. Métis employees were increasingly barred from advancement. Simpson tried to centralize operations at several regional posts - although he soon found it necessary to re-establish several small posts, especially in the north. The larger posts were prominent during the 1800s; however, they were not centred on trapping grounds. Instead, they became important stops along the rapidly developing travel routes leading west to the Pacific and north to the Arctic. Cumberland House (est. 1774), the oldest community in Saskatchewan, retained its importance since it adjoined two crucial transportation routes: the Saskatchewan River, leading west, and the Sturgeon-weir, leading to the Athabasca country by way of the Churchill River. Carlton House (est. 1810) and Fort Pitt (est. 1829), on the North Saskatchewan River, began as provisioning posts, but both became important way-stops on the newly developing Carlton Trail between Red River and Fort Edmonton. Fort Pelly (est. 1824), on the upper Assiniboine River, was the gateway for the trade on the northeastern plains, but it became a backwater as the bison retreated further west. The focus shifted to Fort Ellice (est. 1831), near the junction of the Assiniboine and Qu'Appelle Rivers, which became important for both travelers on the Carlton Trail and for Métis who were traveling out onto the plains. Ile-à-la-Crosse (est. 1776), the only major post in northern Saskatchewan, and the second-oldest community, was an important stop along the Portage la Loche route and the terminal for the Green Lake Trail, by which pemmican was brought from the south.