According to the United States Census Bureau, the city has a total area of 17.4 square miles (45 km2), of which 9.8 square miles (25 km2) is land and 7.6 square miles (20 km2) is water. The total area is 43.79% water. Menlo Park is long and narrow on a northeast to southwest axis. The northeast portion borders the San Francisco Bay and includes the Dumbarton Bridge that connects Menlo Park to Fremont on the east side of the bay. The city shoreline includes the city's largest park, Bedwell Bayfront Park 160 acres (65 ha) and the Don Edwards San Francisco Bay National Wildlife Refuge. San Francisquito Creek marks much of the southeast border of the city. West Menlo Park (not part of the city despite its name) along Alameda de las Pulgas nearly separates the southwestern part of the city (known as Sharon Heights) from the rest. The extreme southwest is clipped by Interstate 280.
The Bayshore Freeway (part of U.S. Route 101) traverses Menlo Park northwest to southeast near the shoreline and somewhat parallel to it to the southwest is El Camino Real. The intersection of El Camino Real and Santa Cruz Avenue is considered the heart of the city. Nearby, the Menlo Park Civic center is bounded by Ravenswood Avenue, Alma Street, Laurel Street and Burgess Drive. It contains the council offices, library, police station and Burgess Park which has various recreational facilities. Other major roads include Sand Hill Road in the Sharon Heights area.
The residential areas of Menlo Park are unofficially divided into several neighborhoods. Belle Haven is the only neighborhood east of the Bayshore Freeway; much of the rest of that area is business or protected land. Between Middlefield road (a road almost parallel to Bayshore) and Bayshore are the neighborhoods of the Willows, Suburban Park, Lorelei Manor, Flood Triangle, Vintage Oaks, and South of Seminary (the seminary being Saint Patrick's Seminary). Between Middlefield and El Camino Real are Felton Gables, Linfield Oaks, and Park Forest. West of El Camino Real until the hills are the neighborhoods of Downtown Menlo Park, Central Menlo Park, and Allied Arts (sometimes also known as Stanford Park, it is named for the Allied Arts Guild in it). In the hills are Sharon Heights and Stanford Hills. Several other neighborhoods are closely associated with Menlo Park but are actually in unincorporated San Mateo county; these include Menlo Oaks and Fair Oaks (latter part of the North Fair Oaks census area) between Bayshore and Middlefield, University Heights (also known as West Menlo Park) between Sharon Heights and most of the rest of the city, and Stanford Weekend Acres which is somewhat near Stanford Hills.
In 1851 two Irish immigrants, Dennis J. Oliver and his brother-in-law D. C. McGlynn, purchased a 1,700-acre (690 ha) tract of land on the former Rancho de las Pulgas. In 1854, they erected a gate with a wooden arch bearing the inscription "Menlo Park" and the date "August 1854" at the entrance to their property (now the intersection of Middle Ave and El Camino Real). The word "Menlo" derived from the owners' former home of Menlo in County Galway, Ireland, and is an Anglicized version of the original Irish name of the place, Mionloch, meaning "middle lake."