San Antonio’s I-35/I-37 interchange, 1971Build it around the traffic.

Try following just one ramp in the aerial photograph. Before long it crosses another, slips past a building or joins a road already carrying traffic. This was a difficult place to build a tidy, symmetrical interchange. The city was there first.

Frank G. Kelly Jr.’s June 1971 feature described the $11 million I-35/I-37 interchange as a key part of a second freeway loop around San Antonio’s central business district. Construction had begun in July 1969. Roughly ten district engineers had spent almost eight months preparing the plans, using tools that ranged from slide rules to the department’s computer in Austin. Kelly’s design and construction account

The aerial view gives that planning effort a setting. Existing streets, businesses and the curves of I-35 occupy the space beneath and around the new ramps. District Engineer Robert Lytton contrasted the design with a conventional, symmetrical cloverleaf. The unusual shapes answered a particular location; they were not complexity added for its own sake.

The San Antonio historic photograph collection places this project among earlier roads and later construction. The interchange photograph is especially useful because it shows both the new structures and the city they had to fit.

At ground level, the problem became much more immediate: where could a crane stand, and how could crews place a long girder while the surrounding road remained in use? The magazine’s construction photograph shows a suspended steel member, workers beside the structure and completed supports waiting for the next piece.

Project engineer Richard Magers put the constraint plainly: We had to work over, under, and around traffic. Kelly reported that construction was being arranged to avoid interrupting I-35’s traffic flow. That describes the project’s objective, not a claim that drivers never encountered a closure or delay. The working-road problem

Steel served a specific purpose here. Kelly explained that the longer spans used steel girders instead of prestressed concrete beams and estimated that the structures would contain about 13 million pounds of structural steel. A longer span could cross more of the roadway without another support in the middle. The choice affected both the finished interchange and the work of putting it together.

The picture also separates stages that can disappear in a finished-road photograph. A line of columns is not yet a bridge deck, and a girder hanging from a crane is not ready for traffic. Each new connection depended on the pieces beneath it being in place.

The Tower of the Americas rises behind another construction view. Below it, a row of bare supports runs alongside cars on a city street. The magazine identifies the location as Durango Street near the HemisFair grounds and gives March 1972 as the expected completion date for that last section of I-37 in Bexar County. This was the remaining approach, not a photograph of a fully connected freeway.

The planned interchange and adjoining I-37 work were intended to provide freeway access to downtown from the east and complete the inner loop. Kelly repeated a forecast that the combined projects would draw about 100,000 cars from city streets. It is a prediction in an enthusiastic agency feature; these construction photographs cannot tell us whether that traffic estimate was achieved. The adjoining freeway and traffic forecast

Driver protection also received attention. Kelly described plans for impact attenuators at two locations. These were intended to reduce the consequences of striking fixed obstacles. A later Texas Transportation Institute retrospective places the Texas Crash Cushion’s development in the 1960s, showing that this project belonged to a wider period of roadside-safety experimentation. TTI’s safety-research retrospective

The I-37 road photographs provide other views of the corridor. Here, with the supports exposed, it is easier to see how many separate tasks lay between drawing a connection and giving drivers a continuous route.