Complex sentence: Shropshire was established during the division of Saxon Mercia into shires in the 10th century and after the Norman Conquest experienced significant development, after the principal estates of the county were given to eminent Normans.
Split into simpler sentences: Shropshire was established during the division of Saxon Mercia into shires in the 10th century. After the Norman Conquest it experienced significant development, following the granting of the principal estates of the county to eminent Normans.