[7] The city was named in honor of Charles Merriam, a one-time secretary/treasurer of the then Kansas City, Fort Scott and Gulf railroad (later the St. Louis–San Francisco Railway) which ran through the area.

Shawnee Mission Parkway, an east–west road, nearly bisects the city.

Turkey Creek, following a roughly parallel path to the Interstate, flows through the city.

According to the United States Census Bureau, the city has a total area of 4.32 square miles (11.19 km2), all land.

[10] The 2020 United States census counted 11,098 people, 5,070 households, and 2,762 families in Merriam.

There were 5,297 housing units at an average density of 1,227.0 per square mile (473.7/km2).

37.3% of households consisted of individuals and 12.6% had someone living alone who was 65 years of age or older.

[16] The percent of those with a bachelor's degree or higher was estimated to be 29.8% of the population.

[20][21] As of the census[22] of 2010, there were 11,003 people, 4,900 households, and 2,788 families living in the city.

There were 5,224 housing units at an average density of 1,209.3 per square mile (466.9/km2).

34.9% of all households were made up of individuals, and 9.4% had someone living alone who was 65 years of age or older.

As of the U.S. Census in 2000,[24] there were 11,008 people, 4,839 households, and 2,903 families living in the city.

33.3% of all households were made up of individuals, and 7.6% had someone living alone who was 65 years of age or older.