First Americans in Los Angeles, by Margaret Romer, 1924

"On Christmas Day in the year 1828 the American brig 'Danube' was wrecked on the rocks at San Pedro. The crew were rescued and a few of them remained as settlers. Among these was John Groningen, a German. The Spanish people could not twist their tongues around the name so they called him Juan Domingo."

Many Famous Fourths Held in Los Angeles, by George W. Kirkman, 1927

"Many famous Fourths has our ancient city seen, in its dramatic and colorful history; but some of them were epochal enough to have deep interest and special significance to all Angelenos."

Artist’s sketch of Juan Domingo residence

"Artist's sketch of Juan Domingo's large adobe home and vineyard located on the corner of Alameda and Aliso streets. Domingo's real name was Johann Gronigen, a native of Holland who came to America as a ship carpenter. He settled in Los Angeles, and by reason of his arrival in town on a Sunday, and the difficult pronunciation of his German name, the natives called him Juan Domingo."