The Poplar River is a tributary of the Missouri River

Missouri River

The Missouri River flows through the central United States, and is a tributary of the Mississippi River. It is the longest river in North America and drains the third largest area, though only the thirteenth largest by discharge. The Missouri's watershed encompasses most of the American Great...

, approximately 167 mi (269 km) long in Saskatchewan

Saskatchewan

Saskatchewan is a prairie province in Canada, which has an area of . Saskatchewan is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, and on the south by the U.S. states of Montana and North Dakota....

 in Canada

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

 and Montana

Montana

Montana is a state in the Western United States. The western third of Montana contains numerous mountain ranges. Smaller, "island ranges" are found in the central third of the state, for a total of 77 named ranges of the Rocky Mountains. This geographical fact is reflected in the state's name,...

 in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

.

It rises in several forks on the plains of southern Saskatchewan. The western fork rises near Killdeer, Saskatchewan and flows southeast, into northeastern Montana, past Richland and across Daniels County

Daniels County, Montana

-Economy:The main source of income for Daniels County has been cattle and dryland wheat.-Demographics:As of the census of 2000, there were 2,017 people, 892 households, and 561 families residing in the county. The population density was 1.4 people per square mile . There were 1,154 housing units...

. The middle fork rises northwest of Rockglen, Saskatchewan

Rockglen, Saskatchewan

Rockglen, Saskatchewan, Canada, is a community in the Burning Hills of the Wood Mountain Uplands, providing a school, community hall, public library and five parks, as well a local service industry. The municipal office of Rural Municipality #12 Old Post lies within the boundaries of Rockglen, and...

 and flows southeast, into northeastern Montana and passes west of Scobey

Scobey, Montana

As of the census of 2000, there were 1,082 people, 500 households, and 280 families residing in the city. The population density was 1,481.6 people per square mile . There were 611 housing units at an average density of 836.6 per square mile...

. The two forks unite in the northern Fort Peck Indian Reservation

Fort Peck Indian Reservation

The Fort Peck Indian Reservation is near Fort Peck, Montana. It is the homeland of the Assiniboine and Sioux tribes of Native Americans. It is the ninth-largest Indian reservation in the United States and comprises parts of four counties. In descending order of land area they are Roosevelt, Valley,...

. The combined fork flows SE, then SSW, and joins the Missouri near Poplar

Poplar, Montana

As of the census of 2000, there were 911 people, 325 households, and 206 families residing in the town. The population density was 3,406.0 people per square mile . There were 350 housing units at an average density of 1,308.5 per square mile...

.

Along with the Milk River

Milk River (Montana-Alberta)

The Milk River is a tributary of the Missouri River, long, in the United States state of Montana and the Canadian province of Alberta. Rising in the Rocky Mountains, the river drains a sparsely populated, semi-arid watershed of , ending just east of Fort Peck, Montana.-Geography:It is formed in...

 and Big Muddy Creek, it is one of three waterways in Canada that drain into the Gulf of Mexico.

Variant names

The Poplar River has also been known as: Lost Child Creek and Middle Fork Poplar River.