The Waco line was the longest interurban line in the world.  It also was opened in 1913 with holiday glee.  The Waxahachie mayor drove the final spike on September 30, with high ceremony.  Nine special trains made the run to Waco with stops for speeches and box lunches at towns on the way.  In Waco that night the town was ablaze with with light.  Bands played in streets thronged by thousands of people.  Red fire blazed from the roof of one of the town's tallest buildings, and bit guns and anvils roared.

For a time, the new road prospered, but modern highways, buses, autos and trucks began to take its business.  Since the company was reorganized in 1936, it had made a profit only during the war years.  The Texas Electric Railway's interurban line was discontinued in 1934.  TP&L Company made a trade with Texas Electric Railway, James P. Griffin, receiver, whereby TP&L acquired certain property, the larger portion of which was jointly used with the railway, in exchange for claims held by the Company for electric service furnished the railway prior to receivership.  For a small cash consideration, the major items of property acquired were the McKinney power plant, which TP&L had held under lease for several years, eight brick substation buildings and lots, all containing equipment; the pole line supporting the company's 33,000 volt transmission line from the Jenkins substation near Vickery to the Payne substation near Sherman; a building lot in Corsicana, and several thousand miscellaneous poles, together with the necessary easements along the right of way of Texas Electric Railway.

The company contracted with Southwestern Gas & Electric Company (later Southwestern Electric Power Company) in 1931 for the sale of 19,000 kilowatts to that company at a point east of Tyler, thus making effective use of the additional generating capacity added at Trinidad.  A new 67-mile 132,000-volt transmission line was built from Trinidad to serve this load, a part of 189 miles of transmission lines were converted from lower voltages to 132,000 volts during 1931 to permit more economical transmission of large blocks of power into the northern and southern sections of the area served.

The period from 1930 through 1939 was marked by the development of the territory already served by transmission lines and by the building of rural lines.  At the end of 1939, Texas Power & Light had in operation some 1,900 miles of high-voltage transmission lines and 7,500 miles of low-voltage and rural lines, with service to more than 135,000 customers.  By that time all cities and towns served by the company had transmission line service available.