The plaque reads: 
<p>G. H. &amp; H. R. R. UNDERPASS
BUILT IN 1936 BY THE
TEXAS HIGHWAY DEPARTMENT
</p><p>UNITED STATES
BUREAU OF PUBLIC ROADS
</p><p>STATE HIGHWAY COMMISSION
HARRY HINES           CHAIRMAN
D. K. MARTIN                 MEMBER
JOHN WOOD                 MEMBER
GIBB GILCHRIST
HIGHWAY ENGINEER
RUSS MITCHELL, INC,
</p>
CONTRACTOR
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/32345848@N07">Patrick Feller</a> from Humble, Texas, USA
CC BY 2.0
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/nakrnsm/8169393075/">N. Wayside at GH&amp;HRR (Union Pacific RR) Underpass, Houston, Texas 1204101608BW</a>