Final answer:
Kentucky's bluegrass region was named for the blue-flowered Poa grass. This area is known for its fertile soils and is important in horse breeding and racing.
Step-by-step explanation:
The state's bluegrass region that was named for the blue-flowered Poa grass that grew there is Kentucky. The bluegrass region is characterized by fertile soil, and the Poa grass, or bluegrass, lends its name to the region due to the bluish-purple buds that appear when it is ready to seed, giving a blue hue to the grass in spring.
This region is not only noted for its agricultural suitability but also its significant role in horse breeding and racing.