San Mateo County extends from the south line of the City and County of San Francisco to the San Francisquito Creek and a line extending westerly from the source of this creek over the San Morena Range to the Pacific Ocean and out to a distance of 3 miles. Its eastern boundary is the bay of San Francisco; and its western boundary is the Pacific Ocean. Santa Cruz and Santa Clara Counties are adjacent to the southern boundary line.

The area of the county is 447 square miles out of the peninsula’s total area of 550 square miles. The extreme distance between northern and southern boundaries is 41 miles and that from cast to west is 18 miles. The county’s narrowest width is found up toward the northern extremity where it is but five miles from bay to ocean. On the south, the irregular boundary formed by Santa Cruz and Santa Clara Counties is about 65 miles. The County’s greatest area is between the San Morenas and the bayshore.

This land slopes almost uniformly from the mountain crests to the bay, and is interspersed with valleys. One of these, the Canada de Raymundo, the most extensive of the county’s interior valleys, runs parallel to the San Morenas and inside a range of foothills to the east. There are other smaller valleys throughout the San Morena Range, of which the shallow valleys flaring out at its base, and sheltering the towns of San Carlos, Belmont and Burlingame are the most important.

Upon the coast side, the San Morena Mountains drop to the sea in steep declivities and cliffs with very few gradual descents. This range, with its average height of 1200 feet, gradually increasing southward to a point back of Searsville where the altitude is about 2,500 feet, extends north and south through the county and divides it into two parts,-the bayside and the coastside. The San Bruno Hills which are a part of the San Morena Range extend at right angles to the bay from this range, running between San Francisco and South San Francicso. The San Bruno Hills are pierced here by five tunnels constructed by the Southern Pacific Company at an expense of $7,000,000.

Near the northern border of the county, the summit of the San Morenas is seen to be split in a line from north to south. Here lies a tableland or shallow valley in whose center extends a picturesque chain of three artificial lakes, Pilarcitos, San Andreas and Crystal Springs.

Few counties of the state are better supplied with lakes and streams than San Mateo County. San Francisquito Creek, which for a long distance is the dividing line between San Mateo and Santa Clara Counties, has its source in the foothills and empties in the southern extremity of San Francisco Bay. Northward of this are courses of considerable carrying capacity in the rainy season, but dry in summer. These include the bed of the San Mateo Creek which flows through the city of San Mateo, and is the second in size on the bay side of the county.

On the coast side of the county from north to south, are the San Pedro, Denniston, Frenchman’s, Pilarcitos, Purissima, Lobitas, Tunitas, San Gregorio, Pomponio, Pescadero, Gazos and White Horse Creeks, all of which are filled with water during the summer months. Waddell Creek is just beyond the county line .

The best fishing is in the Purissima, San Gregorio, Pescadero and Gazos Creeks.

The Pilarcitos, Purissima, San Gregorio, Pescadero and Gazos are the largest and most important of these coast streams. The San Gregorio, Pescadero and Gazos Creeks are fed by tributaries. The tributaries of Pescadero Creek are the Butano (in turn fed by the Little Butano) and Peters and Rock Creeks. The Pescadero Creek is the longest in the county and has the most extensive watershed. The tributaries of the San Gregorio are the Borgess, Corte Madera, Herrington, La Honda, Mindege, and Alpine Creeks..

Bays are a feature of the coast that add considerably to its attractiveness. Halfmoon Bay is the deepest indenture upon the county coast line. At Seal Rocks the land extends seaward in the form of a hook, and from here to the southward for a distance of about 6 miles in a gradually widening half moon-like curve, the formation of the bay exists, growing less and less prominent. At the mouth of the Pilarcitos, San Gregorio and Pescadero Creeks are little lagoons where the fishing is good. Where the Arroyo de las Frijoles flares out on the ocean shore, in the southern extremity of the county, there is also a lagoon..

The Great Basin, an attractive portion of which lies in the southern part of the county, with its eternal giants of the forest, and rushing mountain streams, is another spot still unprofaned by the hand of man and little marred by fire. This big preserve lies directly between Los Gatos and Pescadero, and is reached by a delightful drive of twenty-five miles from the Ocean Shore Railroad’s present terminus at Tunitas Glen.

Upon the map published by the United States Geodetic Survey can be seen a wide channel of deep water extending to Hunter’s Point from Dumbarton. Redwood Creek opens into this channel, thereby guaranteeing this city unlimited water transportation to San Francisco and other points, when the intervening arm’ of the sea has been properly dredged and straightened. This natural channel skirts the bayshore, upon which there are four places where wharves can be cheaply constructed for the accommodation of deep water ships: South San Francisco and San Bruno Point nearby, where the channel has already been enlarged and a turning basin created, Coyote Point near San Mateo, and Redwood Point near Redwood City.

The bayshore of the county located a few miles east of the railroads with its thriving communities, is for the most part, a low lying area. The bayshore winds in and out in a series of complicated and involved curves. Before this land can be used for residential or manufacturing purposes it must be reclaimed and filled in, to a depth of almost six feet, which will make it very valuable for farming land, homesites, of industrial purposes, and repay many times over the expense of reclamation.

Extending along the bay shore from a point near Lomita Park to beyond San Mateo, are located a number of oyster beds covering an extensive area and projecting several miles out into the bay. The greater portion of these belong to the Morgan Oyster Company, although much of this territory is apportioned off in private ownership ; the D. O. Mills Estate in particular holding thousands of acres of this valuable marsh land.

The oysters produced are classed as Eastern oysters, are of a high quality and command a good price in the San Francisco markets.

In direct contrast to the bayshore, the ocean side of the county presents an aspect of beauty as well as usefulness. For the entire length of the county’s ocean sweep of fifty-five miles there is an almost unbroken stretch of beautiful beach, winding in gentle curves to the south, and admirably adapted to recreation and suburban homes. This frontage added to the thirty-five miles of bay frontage, gives the county a total water frontage of ninety miles.