The Glagolitic Script was used in the Great Moravian Empire in the 9th century, and was the first known Slavic alphabet. So where was Moravia anyway? I didn't even know so I looked it up.
Moravia was the first Slavic state, and encompassed the area that is now the Czech Republic, Slovakia, Poland and Hungary. After Moravia fell in the 10th century, Glagolitic had spread across the region and continued to be used, particularly in Croatia, until the 12th century.
The Baska Tablet
The Glagolitic script
“The Great Moravian Empire fell in the early 10th century.”