Although these natives are mentioned frequently in the correspondence of the period, the first recorded exploration of their area was that of Fr. José Viader in 1810. This missionary left Mission San Jose on August 15 and went by way of Pittsburg and Antioch to the mouth of the San Joaquin, whence he traveled southeast to Pescadero, "... la rancheria de los Cholvones." Leaving the rancheria he went on up the river. Viader's second expedition was carried out during the month of October of the same year. This time he went directly from San Jose to Pescadero, which he says was 15 leagues northeast to east-northeast of Mission San Jose. The account at this point is not particularly lucid. The entry for October 20 states that at Pescadero the gentiles were having a dance (bayle). That for the following day begins with the statement that at dawn Viader's party attacked "... asaltamos una rancheria de este lado del rio y solo escapo un Christiano ..." Then they attacked another rancheria on the other side of the river and captured 15 Christians and 69 gentiles. From the context it may be inferred that the first rancheria attacked was the one at which the dance was being celebrated on the evening of the 20th, that is to say, Pescadero. If it was, then there was another, quite sizable, village just across the river. If the first village was not Pescadero, then there were two other villages in close proximity to it. The next visitor was Fr. Ramon Abella, who left San Francisco by boat on October 15, 1811. Passing Sherman Island on the 18th and wandering erratically through the swamps he reached the "tierra de los cholbones" on the next day. On October 20 he reached the village of Pescadero but made no comment on it in his diary. After examining the territory of the Cosmistas and Boyboses 5 to 15 miles to the east, the party turned about 8 to 9 miles (3 leagues) northwest, following the general trend of the river downstream. At this point they found a rancheria of 900 persons "divididas en tres rancherias, alguna distancia una de otras. No vimos que la una: Se presentan como 150 personas ... y nos enseñaron al desembarcadero y las mismas casas que havía duplicado gente ..." Abella's distances are extremely inaccurate but it is apparent that the three villages mentioned were north or northwest of Pescadero.