The Fort is no longer standing, but it was originally built in 1849.
From Wikipedia:
In January 1849 Worth proposed a line of ten forts to mark the Western Texas frontier from Eagle Pass to the...
It's about 20-25 miles or 15/20 minutes; technically, though, the distance is zero. An arm of the city of Fort Worth stretches east (between Hurst-Euless and Arlington) all the way to the southern...