It was a fair and fertile land.
It was once the original home of all the Hobbits before they migrated into the west to the lands of Bree, Dunland, and finally the Shire due to increasing danger coming from Mirkwood. A colony of Stoor hobbits remained in the Gladden Fields until something after TA 2460.
By the latter part of the Third Age, this land was for the most part deserted due to the dread of Mirkwood. Only the Beornings, including Beorn himself, the Woodmen and Radagast at Rhosgobel dared live in or near this land.