Ialomița County has a total area of 4,453 km2 (1,719 sq mi). The county is situated in theBărăgan Plain. The area is flat crossed by small rivers with small but deep valleys.
Its eastern border is on theDanube. TheIalomița River crosses the county from West to East about the middle. The Danube is split around theIalomița Pond into the Old Danube branch and theBorcea branch.
Until 1940 (in the western part) and 1967 (in the eastern part) the county/plain was home of thegreat bustard (dropie inRomanian), with large populations of this bird. The birds disappeared because of the massive village buildout and hunting them for food.
Historically, the county was located in the southeastern part of Greater Romania, in the southeastern part of the historical region ofMuntenia. The county comprised a large part of the current Ialomița County and of today'sCălărași County. It was bordered to the west byIlfov County, to the north by the counties ofPrahova,Buzău andBrăila, to the east byConstanța County, and in the south byDurostor County.
With an area of 7,095 square kilometres (2,739 sq mi), Ialomița County was one of the largest counties of Greater Romania.
According to the 1930 census data, the county population was 293,352 inhabitants, ethnically divided as follows: 96.6% Romanians, 2.5% Romanies, 0.2% Jews, as well as other minorities. From the religious point of view, the population was 99.3% Eastern Orthodox, 0.2% Jewish, 0.1% Roman Catholic, as well as other minorities.
In 1930, the county's urban population was 34,260 inhabitants, comprising 90.2% Romanians, 6.0% Romnanies, 1.3% Jews, as well as other minorities. From the religious point of view, the urban population was composed of 97.4% Eastern Orthodox, 1.4% Jewish, 0.5% Roman Catholic, as well as other minorities.