Why was it so important to the South’s Civil War effort that Texas maintain control of its ports?

They use the ports to send supplies to their troops and sells their agricultural products

Explanation:

This means that if the northern army managed to conquer the Southern Ports during the civil war, they can intercept the South's product distribution and food/weapon supplies for their army.

Knowing this, the Union decided to sent their navy in order to blockade southern ports. This eventually cripple's the South's economy and made their troops weaker due to hunger. This contributed to their loss in the Civil War.

At the time of the Civil War, the South had an agriculturally-based economy and there were no manufacturing plants. All of the manufacturing plants that produced things like shoes, clothes, ammunition, and food were in the North. Therefore, when the war began, the South had to rely on receiving goods and supplies from the outside – from their trade partners in Europe. The South did not have enough of their own supplies to last through a long war. Therefore, ports throughout the South became very important as a way of keeping troops and families alive. One of the main ways for goods to reach the Confederacy was through Texas ports. The Confederate coast was lengthy and difficult for the Union to shut down. A key role for Texans was to keep its ports open and free from Union control.

they required less loading and unloading

explanation:

the shipping container improved shipping because it cut down on unloading time by three weeks, eliminated wasted space, and allowed ships to carry.