The area is in the Cucamonga Wilderness in the San Bernardino National Forest, 1.24 miles south of Bonita Falls on South Fork Lytle Creek and north of Rancho Cucamonga, California.

When the American Civil War ended in April with Lee's surrender at Appomattox the gang with a price on their heads, came under pressure from the Union Army and law enforcement officials in Central California.

[2][3] The flat was named (but misspelled) for Don Pedro Sainsevain, who with his brother bought part of Rancho Cucamonga in 1865 and set out a large vineyard.

He moved to Cucamonga in 1870 and ran the vineyard and winery with Joseph S. Garcia.

In 1874 the Sainsevain brothers purchased land in Hawker Canyon four miles east of Etiwanda and built a large stone house and a reservoir there.