Rivera worked for 15 years for Merrill Lynch, Pierce, Fenner & Smith.

Rivera began his political career in 1968, when he was elected as member of the Municipal Assembly of Bayamón.

After one term as Representative, Rivera ran for Mayor at the 1976 general election.

During his 24-year tenure, many buildings and other types of structures were inaugurated, including the Parque De Las Ciencias, the Parque del Trensito (which had, at the time it opened, Puerto Rico's only running train and a DC-3 plane formerly used by United Airlines), the city hall, which is a building that crosses over an avenue, the Ruben Rodriguez Coliseum, the Canton Mall, a small, pedestrian suspension bridge at Lomas Verdes neighborhood and many others.

In addition, a large industrial park with such notable companies as 7 Up and Wrangler also opened, in the area known as Lomas Verdes.