[4] This area on the east side of Mount Diablo was historically the homeland of the Volvon, one of five tribes in the region who spoke dialects of the Bay Miwok language and were encountered by Spanish explorers.

The Spanish began exploring and colonizing the area east of San Francisco Bay in 1772, which resulted in wholesale changes to the world of the Volvon and other regional tribes.

Unsanitary conditions at the missions and exposure to new infectious diseases carried by the foreigners caused the deaths of many Native Americans.

After Mexico gained independence from Spain in 1821, it continued the practice of granting large ranchos to Californios on Bay Miwok homelands, beginning in the 1820s.

On April 17, 2015, BRPD announced that it had added a 260 acres (110 ha) parcel of land, formerly called the Viera farm, to the Morgan Territory Regional Preserve.

To illustrate the proposal, he built a large, three-dimensional model of the main ridge and headwaters of Marsh Creek, which were the most prized areas.

Hulet Hornbeck, Chief of Acquisitions for the EBRPD, collaborated with Lindner to persuade the District Board of Directors to create the Preserve.

The population of the nearby Tri-Valley had already begun to increase, a trend that continued in the following decades, driven by expansion of technology firms and related businesses in the Silicon Valley and region.

[citation needed] In the late 1980s and early 1990s, Bob Walker (1952-1992), an environmentalist, photographer, and president of the Sierra Club San Francisco Bay Chapter for a period, led efforts to expand the preserve from its initial 970 acres (3.9 km²).

He had succeeded Hornbeck as Assistant General Manager and Chief of Acquisitions for the East Bay Regional Park District.

Seth Adams, staff for Save Mount Diablo, aided Walker and Doyle in the long-term goal to protect natural areas in the region.

In 1989 Save Mount Diablo bought the 631-acre (2.6 km²) Morgan Territory Ranch from descendants of the pioneer settler, placed a conservation easement on it, and transferred the property to Mt.

[citation needed] Following that, in 1994 the state created the 30-mile (48 km) Diablo Trail, which runs across six parks from Walnut Creek to Brentwood.

[citation needed] On April 17, 2015, EBRPD announced that it had acquired and added a 260 acres (110 ha) parcel of land, formerly known as the Viera farm, to the Morgan Territory Regional Preserve.

[7] Prolonged heavy rains during the winter of 2016-2017 caused significant flooding and damage to park facilities, especially roads and trails.