"[4] A portion of the Carretera Central from partway through Caguas to the end of Juana Díaz was listed on the U.S. National Register of Historic Places in 2019.

[2]: 7 [7] In the 1820s, the Spanish colonial government in Puerto Rico, under the direction of Governor Miguel de la Torre took the first steps for building a highway connecting the towns of San Juan and Río Piedras[b] and incorporating temporary wooden bridges for river crossings.

[2]: 4 During the 1830s an unpaved wagon road was built linking Ponce, Juana Díaz and Coamo to satisfy the commercial sugar production needs of that area.

[2]: 4  In 1846 a new masonry bridge was built by Spanish engineer Santiago Cortijo to connect the capital city island of San Juan with the rest of the Puerto Rico mainland.

[2]: 6 The then-municipal highways connecting Ponce, Juana Díaz and Coamo were made part of the state-run Carretera Central between 1875 and 1880.

[2]: 12 As one of the first modern roadways in Puerto Rico, being built from 1846 to 1886, and regarded as one of the finest roads in the Americas for years after its completion, a portion was listed on the National Register of Historic Places in 2019.

The listed portion of the road, from Caguas to Juana Díaz, includes the exceptionally challenging engineering through the Cordillera Central, 11 major bridges, 14 maintenance workers' houses,[c] and numerous other roadway structures.

[6] Note: kilometer markers represent the distance along the current Puerto Rico numbered highways rather than the original Carretera Central.