When the columns’ contents are reordered correctly, the grid gives a series of events that occurred in the 90s of different centuries. Order them by the century, then index the one’s digit into the event name.
999 BIRTHJUSTICEBAO 9 T
1096 THEFIRSTCRUSADEBEGINS 6 R
1192 BEGUNFIRSTSHOGUNATE 2 E
1299 FOUNDINGEMPIREOTTOMAN 9 E
1398 THEEMPERORHONGWUDIES 8 R
1492 COLUMBUSSETSSAIL 2 O
1599 COMPLETEDGLOBETHEATER 9 D
1692 BEGUNSALEMWITCHTRIALS 2 E
1793 KINGLOUISXVIEXECUTED 3 N
1892 STRIKESINHOMESTEAD 2 T
This gives us the clue phrase TREE RODENT, which is more commonly known as a SQUIRREL.