Lodge Grass is located at . According to the United States Census Bureau, the town has a total area of, all of it land. A traditional camping area near the town is called Iishipia in the Crow language.
As of the census of 2010, there were 428 people, 114 households, and 95 families residing in the town. The population density was. There were 133 housing units at an average density of. The racial makeup of the town was 9.6% White, 86.7% Native American, 0.2% Asian, 0.2% from other races, and 3.3% from two or more races. Hispanic or Latino of any race were 1.4% of the population. There were 114 households of which 59.6% had children under the age of 18 living with them, 43.9% were married couples living together, 26.3% had a female householder with no husband present, 13.2% had a male householder with no wife present, and 16.7% were non-families. 16.7% of all households were made up of individuals and 7.1% had someone living alone who was 65 years of age or older. The average household size was 3.75 and the average family size was 4.05. The median age in the town was 24.7 years. 39.7% of residents were under the age of 18; 10.7% were between the ages of 18 and 24; 20% were from 25 to 44; 20.7% were from 45 to 64; and 8.6% were 65 years of age or older. The gender makeup of the town was 47.2% male and 52.8% female.
2000 census
As of the census of 2000, there were 510 people, 147 households, and 115 families residing in the town. The population density was 2,141.7 people per square mile. There were 164 housing units at an average density of 688.7 per square mile. The racial makeup of the town was 11.57% White, 86.67% Native American, 0.59% from other races, and 1.18% from two or more races. Hispanic or Latino of any race were 1.57% of the population. There were 147 households out of which 57.1% had children under the age of 18 living with them, 47.6% were married couples living together, 27.2% had a female householder with no husband present, and 21.1% were non-families. 18.4% of all households were made up of individuals and 6.1% had someone living alone who was 65 years of age or older. The average household size was 3.47 and the average family size was 3.90. In the town, the population was spread out with 42.4% under the age of 18, 9.6% from 18 to 24, 29.0% from 25 to 44, 13.5% from 45 to 64, and 5.5% who were 65 years of age or older. The median age was 23 years. For every 100 females there were 92.5 males. For every 100 females age 18 and over, there were 77.1 males. The median income for a household in the town was $22,120, and the median income for a family was $22,222. Males had a median income of $20,833 versus $20,375 for females. The per capita income for the town was $8,130. About 37.1% of families and 40.3% of the population were below the poverty line, including 47.4% of those under age 18 and 31.4% of those age 65 or over.
The Lodge Grass city limits and surrounding is located within School District 2 & 27, or Lodge Grass Schools. The public school system has been in existence since 1908. The mascot for Lodge Grass Schools are the Indians and Lady Indians. The Lodge Grass High School boys' basketball program is noted for having won five Class B state championships from 1980 to 1990, under Coach Gordon Real Bird.
