Land for sale in Illinois's Grundy County recently totaled around $35 million and nearly 1,000 acres. Grundy County ranks 29th in the Land of Lincoln for the combined amount of land currently advertised for sale. Of all land for sale in Grundy County, Morris featured the most land for sale. Grundy County is Illinois's 70th largest county (430 square miles). It's located in the Northern Illinois region of Illinois.