Rail joints connect two adjacent (end to end) rails. Starting in the 1810s, 45°or 60°miter joints were used. Then, as an improvement, scarf joints were developed; the two rail ends were notched and bolted together. Splice joints were invented in the United States around 1830 and led to the development of angled joint bars in the 1850s. Angled joint bar design spread quickly, was adopted worldwide, and became the standard that has endured to the present.
