Geography
The Red River Forms Grayson County's Northern Border with Oklahoma
The Red River runs along the top of Grayson County, marking the state line with Oklahoma, and Lake Texoma sits on that border.
Grayson County stretches about 65 miles north of Dallas to the Red River. The river has historically been prone to flooding, and low-lying areas near it or Lake Texoma may be in flood zones. If you are buying property near the river or the lake's upper arms, check FEMA flood maps first.
The river also means some recreational activities cross state lines. Fishing on Lake Texoma spans two state jurisdictions. The Army Corps of Engineers manages land around the reservoir on both sides. Know which state's rules apply before you camp, hunt, or fish.
Source to confirm: Handbook of Texas — Grayson County