Its county seat is Farmington,[2] and its largest city by both population and area is Layton.

The legislature of the provisional State of Deseret defined the county in an October 5, 1850, act, which also designated Farmington as the seat due to its location midway between boundaries at the Weber River on the north and the Jordan River on the south.

With the advent of the Utah Central Rail Road in 1870, a transition to mechanized agriculture and a surge of commerce, banking, improved roads, new water systems, and electrification of homes began.

[7] The Great Salt Lake is surrounded by marshland and mudflats, and lies at an average elevation of approximately 4,200 feet (1,300 m), varying depending on the water level, which can lead to drastic changes in the lake size due to its shallowness.

Summers are dry and hot and winters are cold and wet, but rarely frigid.

Annual precipitation averages between 18 and 25 inches (460 and 640 mm) in the county, with spring being the wettest season and summer the driest.

This occurs when a powerful high pressure system is over Wyoming, and is a frequent occurrence.

They approve, adopt, and amend the budget; they also serve as the legislative body and regulate business licensing in the county's unincorporated areas.

According to the Census Bureau's 2004 American Community Survey, 42.3% of the population work in another county.

The Legacy Parkway and the FrontRunner commuter rail project were built to alleviate this problem.

Davis County's largest employer is Hill Air Force Base.

[42] Other large employers include Davis School District, Lagoon Amusement Park, and Lifetime Products.

The high schools are as follows, showing where they are located: The campus of Davis Technical College is in Kaysville.

The Utah Department of Transportation is currently (2019) upgrading US-89 to a freeway through eastern Layton north to its interchange with I-84 near the Weber County border.

Construction began near the US-89/I-15 interchange in Farmington in 2004, but was soon halted due to a lawsuit filed by environmentalists, who were concerned that the road would harm marshlands along the eastern edge of the Great Salt Lake.

The Legacy Parkway opened in 2008, running from the US-89/I-15 interchange in Farmington southward to connect with I-215 near the border with Salt Lake County.

An extensive trail system, wetland protection measures, and landscaping were implemented along the highway in response to the environmentalist's concerns, in addition to a lower speed limit and a ban of semi-trailer trucks on the highway.

[45] However, this compromise will expire in 2020, and the roadway is expected to begin functioning under normal Interstate System regulations (i.e. trucks and higher speed limits allowed).

[46] In 2008, the Utah Transit Authority opened the FrontRunner commuter rail line from Salt Lake City north to Ogden, serving the length of Davis County with stations in Woods Cross, Farmington, Layton, and Clearfield.