State Highway 321, or SH 321, is a north–south highway in southeastern Texas, starting at US 90 in Dayton and ending at Loop 573 in Cleveland.In Cleveland, SH 321 is also known as Houston Street, providing the main street for downtown Cleveland. It is a two lane urban highway with a left turn lane as it travels throughout Cleveland, until roughly 3/4 of a mile northeast of the city limit. From Loop 573, on southward until junction with SH 105, SH 321 is also known as SH 105.