Hancock Park was formed around a group of tar pits where natural asphalt (also called asphaltum, bitumen, or pitch; brea in Spanish) has seeped up from the ground for tens of thousands of years.

Dramatic fossils of large mammals have been extricated, and the asphalt also preserves microfossils: wood and plant remnants, rodent bones, insects, mollusks, dust, seeds, leaves, and pollen grains.

[6] Harrison Rogers, who accompanied Jedediah Smith on his 1826 expedition to California, was shown a piece of the solidified asphalt while at Mission San Gabriel, and noted in his journal, "The Citizens of the Country make great use of it to pitch the roofs of their houses".

The original Rancho La Brea land grant stipulated that the tar pits be open to the public for the use of the local Pueblo.

[citation needed] There were originally more than 100 separate pits of tar (or asphaltum) but most of those have been filled in with rock or dirt since settlement, leaving about a dozen accessible from ground level.

[8] In 1886, the first excavation for land pitch in the village of La Brea was undertaken by Messrs Turnbull, Stewart & co..[9] Union Oil geologist W. W. Orcutt is credited, in 1901, with first recognizing that fossilized prehistoric animal bones were preserved in pools of asphalt on the Hancock ranch.

In commemoration of Orcutt's initial discovery, paleontologists named the La Brea coyote (Canis latrans orcutti) in his honor.

[14] Among the finds are remains of a saber-toothed cat, dire wolves, bison, horses, a giant ground sloth, turtles, snails, clams, millipedes, fish, gophers, and an American lion.

[14][15] Also discovered is a nearly intact mammoth skeleton, nicknamed Zed; the only pieces missing are a rear leg, a vertebra, and the top of its skull, which was sheared off by construction equipment in preparation to build the parking structure.

As work for the public transit D Line is extended, museum researchers know more tar pits will be uncovered, for example near the intersection of Wilshire and Curson.

[14] In an exploratory subway dig in 2014 on the Miracle Mile, prehistoric objects unearthed included geoducks, sand dollars, and a 10-foot limb (3.0 m) from a pine tree, of a type now found in Central California's woodlands.

[18] In 1913, George Allan Hancock, the owner of Rancho La Brea, granted the Natural History Museum of Los Angeles County exclusive excavation rights at the Tar Pits for two years.

[22] As a result of a design competition in 2019, the Natural History Museum of Los Angeles County chose Weiss/Manfredi over Dorte Mandrup and Diller Scofidio + Renfro to redesign the park, including by adding a pedestrian walkway framing Lake Pitt, which is 3,281 feet (1,000 metres) long.

"[27] Among the prehistoric Pleistocene species associated with the La Brea Tar Pits are Columbian mammoths, dire wolves, short-faced bears, American lions, ground sloths (predominantly Paramylodon harlani, with much rarer Megalonyx jeffersonii and Nothrotheriops shastensis) and the state fossil of California, the saber-toothed cat (Smilodon fatalis).

Microfossils are retrieved from the matrix of asphalt and sandy clay by washing with a solvent to remove the petroleum, then picking through the remains under a high-powered lens.

[40] If these cuts are in fact tool marks resultant from butchering activities, then this material would provide the earliest solid evidence for human association with the Los Angeles Basin.