Originally, the I&GN operated of track from Hearne to Longview, but at its peak it owned of track. As the railroad expanded, it reached Rockdale in 1874 and Austin on December 28, 1876. In 1880, it was extended to San Antonio and, finally, it reached Laredo on December 1, 1881.
The I&GN, like other railroads of its time, had many financial troubles and went into receivership on several occasions. Jay Gould acquired control of the I&GN in December, 1880, but was forced to sell it in the early 1920s. Finally, on March 1, 1956, the I&GN was bought by the Missouri Pacific Railroad Company and became a major part of its network.