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The Lost Lake in Downtown San Jose

Updated: Jul 3, 2021

Around 1912 - 1916, San Jose constructed an artificial lake where the Guadalupe and Los Gatos creeks converge downtown. It was in the area currently next to SAP Center Arena called the Arena Green Park. It was bounded by West St. John Street and Santa Clara street. The dammed waters reached about a half a mile beyond where the two creeks forked into individual tributaries.

Sourisseau Academy
Boating, swimming and fishing were popular activities
Sanborn Fire Insurance Map, Vol 1, 1915
Location of the Dam aand Lakeside Park

Today it's somewhat difficult to reconstruct some of the boundries of the lake due to the construction of the SAP Arena green park areas and the demolition of a significant section of the River Street historic district to make way for Highway 87.

Present day satellite view of the Lake area
Present day satellite view of the Lake area



Everything started around 1912, at the start of Mayor Thomas Monahan's tenure. The city did not have the funds to build the ambitious water park. That's when the San Jose Lake Association was started to raise the $3,000 to finance the construction of a dam and park amentities.

San Jose Mercury News, September 3, 1912

The citizens are beginning to realize that the acquisition of such a “city beautiful” spot will attract many outsiders to the city, in addition to providing a place where the youth of the city may enjoy themselves in a healthful manner, and not seek the poolroom during spare moments. The beds of the two creeks Join at a point which presents a pretty, natural park appearance, which with slight cost could be made into the most beautiful park space in the city. A collapsible dam will be built which will dam the waters back a distance of one-half mile, forming a lake which will be admirable for rowing and deep enough for swimming.


Politics and Engineering

Mayor Thomas Monahan was so supportive that at some point Guadalupe lake became referred to 'Monahan's Lake' in periodicals.

San Jose Mercury, October 27, 1912
San Jose Mercury, October 27, 1912

According to the SJ Mercury article:

The contract, which was signed yesterday calls for a seven-foot dam, which it is calculated will back up the water to San Carlos street in the Guadalupe creek and only to Santa Clara street in the Los Gatos creek, as the latter has a greater profile. The distance from the dam to the junction of Guadalupe and Los Gatos creeks is about 100 yards and the creek is about 115 feet wide at this place. The point running out between the two creeks, which is now the lumber yard of the Hubbard-Carmlchael company, was once the site of Hoffman's Garden a resort which existed about 10 years ago.

Another interesting bit of history is that this was not the first dam at this location. George Prindiville, recalled the history:

...stated that San Jose had an artificial lake above Santa Clara street about 1872. The Orange Mill company ran its machinery by waterpower furnished by Guadalupe creek in those days and a large body of water collected above the dam. This was utilized by boys in the vicinity a a place to sail their boats, and he mentioned several prominent citizens of this city, who were then boys. who had played truant from school to enjoy the cool waters of the lake. The dam was built by Paul Sainsevain, father of Paul Sainsevain who is employed in the assessor's office. William Powers was appointed by the executive committee yesterday to inspect the work of the contractors during the progress of the work until it is completed.

View of the new dam and bed of artificial lake which will be filled with water this week
View of the new dam and bed of artificial lake which will be filled with water this week


Grand Opening

The Guadalupe lake was officially opened on the first Sunday in May of 1914.

San Jose Mercury, April 24,1914
San Jose Mercury, April 24,1914

Per the San Jose Mercury:

The program will embrace boating and swimming matches and water polo, all open to amateurs and cash prizes will be awarded the winners and the seconds. There will be music and other attractions.

From the Sourisseau Academy description of the opening:

On May 3, 1914, San Jose Mayor Thomas Monahan presided at the opening ceremonies of Guadalupe Lake, which would become known as “Monahan’s Lake.” The festivities, accompanied by the St. Joseph Church Brass Band, featured not only a water polo game but also races by swimmers, rowboats, and children paddling washtubs.

There were also great celebrations for the 4th of July as evidenced by the poster below.

San Jose Mercury, April 22, 1914
San Jose Mercury, April 22, 1914
Amateur shipyards have been established in almost every home along the banks of the creek and new rowing boats are being launched almost every day. At the present time are about 25 or 30 small craft on the lake and these are being put to a good use. All the people who viewed the pretty little body of water yesterday were enthusiastic over its possibilities and there will probably be in the neighborhood of a 100 boats on the water In the near future.

Also mentioned:

lake association .......was appointed to arrange for boat floats at various points on the V-shaped lake which provides more than a mile of rowing surface—a half mile on each side of the apex of the acute angle formed by the junction of the two creeks. The peninsula north of West Santa Clara street between the two streams provides an ideal site for a park and it is possible that it will be selected as a place for the anchoring of floats. There is a plan on foot for placing electric lights along the stream, for the accommodation of those who would like evening and night boat rides this summer during the warm weather. There has also been some discussion as to ways and means of building a board walk along the banks of the lake.


Port San-O-Say

A shop owner on River street converted his printing shop into a boat rental business called 'Port San-O-Say'. He named it 'San-O-Say' to phonetically help visitors to the area correctly pronounce the city name. At one point there were up to 100 boats for rent in the lake area. People also paid to have their boats berthed there.

Sourisseau Academy
Sourisseau Academy

Sourisseau Academy
Sourisseau Academy

Sourisseau Academy
Sourisseau Academy


Next Post

Obviously, Monahan's lake and public park space doesn't exist in the same form today. What happened to it in my next post.



Geo: 37.333281, -121.898779


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