The United States Post Office changed the town's name to "Seagoville" in 1910 to prevent confusion with another city in Texas called Sego.

[5] During World War II, the Federal Reformatory for Women in Seagoville was the site of an Immigration and Naturalization Service detention camp for Japanese, German, and Italian Americans classified as "enemy aliens" and women of Japanese and German ancestry deported from Latin America.

[5][6] Internees at Seagoville published a German language newsletter called the Sägedorfer Fliegende Blätter.

[7] The camp housed up to 647 people, and was closed in June 1945, after the internees were either "repatriated" to Japan or Germany, or transferred to Crystal City, Texas.

[9] [11] [12] At the 2020 United States census, there were 18,446 people, 4,283 households, and 3,445 families residing in the city.

Though individuals had offered to pay for the rental costs at Seagoville, the USPS insisted on closing the city post office.

[5] The minuscule Kaufman County portion is served by Crandall Independent School District.

A very small portion of northeast Seagoville is within the boundaries of Mesquite Independent School District.

The one-room log schoolhouse, which featured split-log seating, was constructed around 1867 in the area of the modern-day Heard Park.

[25] The building, a two-story facility with four rooms for upper grades upstairs and four rooms for lower grades downstairs, on land on North Kaufman Street was donated by Ben H. Fly.

The portion in Kaufman County is within the Trinity Valley Community College district.