There were 159 households out of which 32.7% had children under the age of 18 living with them, 58.5% were married couples living together, 11.3% had a female householder with no husband present, and 28.9% were non-families. 25.2% of all households were made up of individuals and 10.1% had someone living alone who was 65 years of age or older. The average household size was 2.60 and the average family size was 3.16.
In the city the population was spread out with 28.6% under the age of 18, 7.7% from 18 to 24, 27.6% from 25 to 44, 24.5% from 45 to 64, and 11.6% who were 65 years of age or older. The median age was 36 years. For every 100 females there were 93.9 males. For every 100 females age 18 and over, there were 95.4 males.
The median income for a household in the city was $187,485, and the median income for a family was $215,983. Males had a median income of $205,423 versus $164,824 for females. The per capita income for the city was $126,857. About 10.5% of families and 13.0% of the population were below the poverty line, including 22.2% of those under age 18 and 16.7% of those age 65 or over.
In 2007 a remarkable description of life years ago in Garrison was published. The book is called Little Heathens: Hard Times and High Spirits on an Iowa Farm During the Great Depression (ISBN 978-0-553-38424-6). It was written by Mildred Armstrong Kalish who grew up in Garrison and became a Professor of English. The book tells of "a time, a place, and a way of life long gone." Elizabeth Gilbert in the New York Times Book Review wrote of Little Heathens: "Not only trustworthy and useful, but also polished by real, rare happiness. It is a very good book, indeed. In fact, it's averyveryverygoodbook."