Spencer was ranked 10th best place to live in the United States by Relocate-America.com's "America's Top 100 Places to Live for 2007."

Spencer is located at 43°8′43″N 95°8′50″W / 43.14528°N 95.14722°W / 43.14528; -95.14722 (43.145318, -95.147209).

According to the United States Census Bureau, the city has a total area of 10.2 square miles (26.3 km²), of which, 10.1 square miles (26.2 km²) of it is land and 0.1 square miles (0.1 km²) of it (0.49%) is water.

As of the census of 2000, there were 11,317 people, 4,842 households, and 3,011 families residing in the city. The population density was 1,118.1 people per square mile (431.8/km²). There were 5,151 housing units at an average density of 508.9/sq mi (196.5/km²). The racial makeup of the city was 97.57% White, 0.14% African American, 0.13% Native American, 1.11% Asian, 0.04% Pacific Islander, 0.34% from other races, and 0.65% from two or more races. Hispanic or Latino of any race were 1.43% of the population.

There were 4,842 households out of which 29.3% had children under the age of 18 living with them, 51.4% were married couples living together, 7.7% had a female householder with no husband present, and 37.8% were non-families. 33.0% of all households were made up of individuals and 15.1% had someone living alone who was 65 years of age or older. The average household size was 2.28 and the average family size was 2.89.

In the city the population was spread out with 23.8% under the age of 18, 8.9% from 18 to 24, 26.7% from 25 to 44, 21.3% from 45 to 64, and 19.4% who were 65 years of age or older. The median age was 39 years. For every 100 females there were 88.0 males. For every 100 females age 18 and over, there were 85.4 males.

The median income for a household in the city was $32,970, and the median income for a family was $43,145. Males had a median income of $30,537 versus $21,709 for females. The per capita income for the city was $19,153. About 7.3% of families and 9.5% of the population were below the poverty line, including 13.3% of those under age 18 and 10.0% of those age 65 or over.

In 2004, the U.S. federal government placed Spencer's downtown business district on the National Register of Historic Places . Also in 2004, the State Historical Society of Iowa certified the Spencer Downtown Cultural District as one of the initial eight such projects across the state. Spencer's proposal for this designation included remodeling the old Spencer Middle School building into a multi-purpose facility with a senior citizen center, affordable housing units, and a restored facade . Future work on the old Middle School project involves restoration of the historic auditorium . Also part of the State Historical Society designation is the city's renovation of its Grand Avenue bridge to include commissioned stained glass plates in an Art Deco style .

Current cultural attractions in Spencer include the Spencer Community Theater, the Parker Historical Museum, public art displays, and the Bogenrief Glass Studio. Arts on Grand is a nonprofit organization supporting local area artists with a gallery shop, exhibits, classes, workshops, tours, fundraising events, and other activities. The Curiel-Reynolds School of Visual Arts (CRVA) relocated from Detroit to Spencer in 2007 .

Spencer is the site of the library where Dewey Readmore Books was the cat in residence from January 18, 1988, until November 29, 2006. His story is told in Dewey, The Small-Town Library Cat Who Touched the World, by Vicki Myron with Bret Witter.