A trading post was established on the site of Elwood in 1852 by Henry Thompson, who in 1856 sold 160 acres to the "Roseport Town company" which had been organized by St. Joseph capitalists. The consideration paid Thompson was $10,000. The town grew rapidly in its early years and was a dangerous rival to St. Joseph. A hotel of 75 rooms was built and enjoyed liberal patronage. In 1858 there were ten stores, all lines of business was well represented. By 1859 the population was 2,000, and the town might have outstripped its neighbor had not the inroads of the Missouri river washing away acres of the best improved property, discouraged capital and enterprise.
The first store was opened by A. N. Campbell, in 1856, and the first sawmill by William High in the same year. The next year Daniel W. Wilder, author of Wilder's Annals of Kansas, opened a real estate office, and James P. Brace was made postmaster of the newly established postoffice. In 1860 the town was incorporated as a "city of the first class." The first company of the first regiment sent into the Civil war by Kansas was organized here.
In 1876 the town was reorganized and an election held which resulted in the selection of J. W. Montgomery as mayor and the appointment of J. R. Stone as city clerk. The population in 1910 was 636. It has a money order postoffice, telegraph and express offices, telephone connections, graded public schools, and a good local trade.
Elwood is located at 39°45'13N, 94°52'42W (39.753544, -94.878345).
According to the United States Census Bureau, the city has a total area of 5.3 km² (2.0 mi²), all land.
As of the census of 2000, there were 1,145 people, 446 households, and 313 families residing in the city. The population density was 217.8/km² (562.9/mi²). There were 494 housing units at an average density of 94.0/km² (242.9/mi²). The racial makeup of the city was 89.08% White, 6.64% African American, 0.26% Native American, 0.44% Asian, 0.35% from other races, and 3.23% from two or more races. Hispanic or Latino of any race were 1.48% of the population.
There were 446 households out of which 37.9% had children under the age of 18 living with them, 49.3% were married couples living together, 15.9% had a female householder with no husband present, and 29.8% were non-families. 25.8% of all households were made up of individuals and 10.8% had someone living alone who was 65 years of age or older. The average household size was 2.57 and the average family size was 3.07.
In the city the population was spread out with 30.9% under the age of 18, 10.2% from 18 to 24, 27.0% from 25 to 44, 20.7% from 45 to 64, and 11.2% who were 65 years of age or older. The median age was 32 years. For every 100 females there were 98.4 males. For every 100 females age 18 and over, there were 88.8 males.
The median income for a household in the city was $28,950, and the median income for a family was $31,136. Males had a median income of $26,103 versus $17,692 for females. The per capita income for the city was $12,601. About 16.3% of families and 17.0% of the population were below the poverty line, including 21.1% of those under age 18 and 17.9% of those age 65 or over.