Yep -- not just in population (fourth), but in developed area. I grew up there (just inside the city limits at the time -- now ZIP 77017). One summer in the 1950s I dated a girl who also lived in Houston (now ZIP 77038). It was over 50 miles to her house from mine -- and that wasn't Houston's largest cross-distance, even then.
Now, the area within Houston's city limits is almost 60% of that of the State of Rhode Island -- and there is no telling how far it is across the present entire Metroplex -- solid wall-to-wall houses, all the way... :-(
You couldn't pay me enough to get me to move back there from our secluded place in the northeastern Texas Piney Woods boondocks!