Complex sentence: The T&P had a significant foothold in Texas by the mid 1880s but construction difficulties delayed westward progress until American financier Jay Gould acquired an interest in the railroad in 1879.
Split into simpler sentences: The T&P had a significant foothold in Texas by the mid 1880s. Construction difficulties delayed westward progress, until American financier Jay Gould acquired an interest in the railroad in 1879.