In 1953, the Puerto Rico Department of Transportation and Public Works implemented a major renumbering of its insular highways.

[1] Before 1953, highway routes were numbered in the 1 to just over 100 range and were distributed randomly throughout the island, resulting in several routes with long road lengths.

[2] The numbering system adopted in 1953, which is in use today, increased the range of route numbers from the just-over-100 to 999, resulting in a decrease in the length of many routes.

[4] The first major roadways in Puerto Rico were built by the Government of Spain.

By 1898, the year when Puerto Rico was ceded by Spain to the United States, 275 kilometers (171 mi) of roadways had been built.