A thirty-acre amusement park was built by the company of San Antonio Heights, with a powerhouse adjoining. Heavy crowds were transported along Euclid Avenue in the early days, for the line connected Ontario with Upland, provided connections between the SP Station at Ontario and the Santa Fe Station at Upland, and cared for the thongs bound for pleasure-seeking at the Park. Euclid Avenue was famous for it divided highway; in the wide center strip was a double line of huge pepper trees, and between the rows of trees, set a grass-covered private way, went the single track of this line.
Owned after electrification by Ontario Electric Company, the line became the property of the Pacific Light & Power Corporation. in a merger in 1908. Mr. William G. Kerckhoff, at that time president of PL&P, energetically pushed the expansion of the O&SA by building its branch to San Bernardino. However, the O&SA was purchased by SP on 13 April 1912 and this line, plus the line from Upland to Pomona, passed into PE hands.
Route: From Ontario Chamber of Commerce at Emporia Street, north on Euclid Avenue, passing the Central School at G Street, the Chaffey Union High School at 4th Street, making a crossing of the Santa Fe main line at 'A' Street, to Pacific Electric Station, Upland; from here the line continued due north on Euclid Avenue to 24th Street (La Cima), were it turned west on private way to San Antonio Heights.
History: Acquired by PE in 1912. In 1914 established as Ontario-San Antonio Heights Line (branch to Pomona separated and became Pomona-Claremont Line at this time). Line cut back to La Cima on 4 July 1924; on 1 November 1924, cut back to Upland. On 6 October. 1928, Ontario-Upland Line abandoned.
Operation: The main function of this line after 1914 was to provide a shuttle service between Ontario and the main line at Upland. This round-about way to get to the Los Angeles area suffered heavily when motor bus operation began on a direct highway route. In the abandonment hearing in 1928, PE produced records which tended to show that this line was hopelessly incapable of earning even operating expenses. Passenger traffic fluctuated widely, as the follow figures show:
| Year | Passengers | Car Miles | Revenue |
| 1913 | 918,728 | 295,840 | $73,491 |
| 1914 | 612,478 | 232,916 | $50,181 |
| 1915 | 184,750 | 74,724 | $8,745 |
| 1918 | 133,239 | 73,528 | $7,019 |
| 1920 | 382,768 | 124,094 | $20,747 |
| 1923 | 363,121 | 124,649 | $27,798 |
| 1924* | 180,418 | 62,099 | $14,180 |
| 1924# | 66,947 | 23,776 | $5,821 |
| 1924% | 35,692 | 11,631 | $3,118 |
| * Ontario-SA Heights. cut back July 3 # Ontario-La Cima Line to October 31 % Ontario-Upland only | |||
As of 1 February 1924, PE public timetables had separate listings for: Upland-San Antonio Heights Line and Upland-Ontario Line. Approximately one hour service was given from Upland to the Park from 5:46 AM to 10:48 PM. Upland to Ontario service was approximately twenty minutes during rush periods, one hour at off peak periods. 34 round trips daily were carded, of which 16 made connections with main line trains.