Texas Towers were radar platforms, similar to oil rigs, used to supplement the aircraft pickets. They were discontinued sometime after tower number 4 collapsed during a storm with 28 casualties.

TT-2 Texas Tower No. 2
George's Shoal, New York, US
Active: 1958-1963
Wikipedia
Fortwiki

TT-3 Texas Tower No. 3
Nantucket Shoal, Mass,
Active: 1958-1963
Wikipedia

TT-4 Texas Tower No. 4
New York Shoal, New York, US
Active: 1959-1961
Wikipedia
Collapsed with loss of 28 people in January 1961.