Professor Emeritus James Mancuso, has a daughter living in Los Angeles, (the second largest city in the USA), and we have visited when he was here in town, so when he came across the following information regarding Los Angeles, he thought it might interest me, and I in turn thought it would interest you.

First let's lay some groundwork. When Spanish occupation of California began in 1769, an exploratory expedition led by Gaspar de Portola to extend Spanish influence northward from Mexico, decided to found a string of Missions, (ultimately 21) from San Diego to San Francisco, along a trial called California's "El Camino de Real", ("The Royal Highway"), with each of these Missions to be a days horseback ride apart.

Much of California's history began with the Spanish Missions, and represent the first arrival of non-Native Americans to California. Every one of the California Missions tell a story about the history of California. All have been, to some extent, restored and can be visited today. 

Now Jim steps in and asserts, that in doing so, they moved through the area now known as Los Angeles. They camped by a river where fertile soil and availability of water for irrigation impressed members of the party. Father Juan Crespi, who accompanied the group, saw the location as having all the requirements for a large settlement. He named the river, El Rio de Nuestra Senora la Reina de Los Angeles de Porciuncula, which means "The River of Our Lady the Queen of the Angels of Porciuncula."

In September 1771 Father Junipero Serra and a group of Spaniards founded the San Gabriel Mission, (about 8 miles East of Los Angeles) in an area inhabited by small bands of Gabrielino Indians, (also in Los Angeles County, they later established the San Fernando Mission)

On September 4, 1781, a company of settlers called "Los Pobladores" were recruited in the states of Sonora and Sinaloa in Mexico with their mission under authority of Governor Felipe de Neve, to establish pueblos in the name of the king of Spain.  The Pobladores, a group of 12 families - 46 men, women and children led by Captain Rivera y Moncada - established a community in the area discovered by Portola, and named it El Pueblo de Nuestra Senora la Reina de Los Angeles de Porciuncula, after the nearby river. 

Over time, the area became known as the Ciudad de Los Angeles, "City of Angels," and on April 4, 1850 became the City of Los Angeles.

Now finally to the point. 

"El Pueblo de (named after "El Rio de") Nuestra Senora la Reina de Los Angeles de Porciuncula", was named in honor of Mary, the mother of Jesus (and mankind's "spiritual mother"). They did not invent the town's name, but "constructed" it from the name of a famous Italian chapel in Assisi, ("Santa Maria degli Angeli di Porziuncola"),  in the home town of the founder of the Franciscan Order of mendicant (begging) friars, St. Francis of Assisi. 

When he founded the order around the year 1200, a little portion of land ("porziuncula" in Italian) was granted to him by an old established religious order (Benedictine, I believe). On the Porziuncula (porciuncula in Spanish) stood the tiny chapel of Our Lady, Queen of the Angels.

But why called ‘Porciúncula’ and why Our Lady of ‘the Angels’? 

Soon after St.  Francis of Assisi  founded the Franciscan Order, he was given a small, ruined chapel by the Benedictines for his repair and eventual use near Assisi, where he later died. It was on a very small piece of property, a small portion—a ‘porziuncola’ in Italian. Later on, this place of worship became a center of pilgrimage, devotion and repentance. A fresco was painted on the wall behind the altar depicting the Blessed Virgin Mary surrounded by angels. Thus the chapel, which is now surrounded and sheltered by a monumental Papal Basilica, took the name: ‘Saint Mary of the Angels at the Little Portion’. 

More precisely,  Angeli di Porziuncola, a basilica that is located in the suburb
(usually designated as Santa Maria degli Angeli) of Assisi, about 5 km in the valley below the city.  The basilica was constructed between 1569 and 1679. It encloses the Porziuncola (the nucleus of the first Franciscan monastery and the place where St. Clare received the Franciscan cowl from St. Francis in 1211) and the Cappella del Transito where St. Francis died on 3rd October 1226.

Like so many of the great architectural patrimony, this building can be appreciated for the architecture, as well as for the religious connections.  There is something to think about when we connect that building to the stunning new cathedral in Los Angeles. 

I need to check out whether of not the official name of the new cathedral also includes the "de Portiuncula" tag!!!

Perhaps also there is some connection between the date of the beginning of the construction of the basilica (1569) and the date that the name was given to the river (1769).

References: 

history - Los Angeles County 
http://lacounty.info/history.htm

Archdiocese History   
http://www.la-archdiocese.org/Framein/lahisten.htm