B737 Undifferentiated or Other Model
Flight Crew Last 90 Days 290; Flight Crew Type 10300
Human-Machine Interface
Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Returned To Departure Airport; Flight Crew Landed As Precaution
Procedure; Human Factors
Climbing through FL260; the Cabin Altitude Warning horn sounded. We accomplished memory items and QRH for Cabin Altitude Warning Horn/Abnormal Pressurization. We returned to our departure airport for Maintenance and to refuel. Upon rechecking the pressurization panel during descent; we discovered we had set 12;660 rather than 1;226.... I did not verify the correct altitude during the Before Start Checklist. I should have looked more closely at the small numbers in the analog windows. I 'saw' what I was expecting to see.Take time to verify every checklist item.  We weren't late or rushed; but I was still lulled into responding to the checklist item as 'correct.'  Checklist item settings are almost always correct; but I need to ensure that I closely check every item; every time; before I respond.
A B737 flight crew returned to the departure airport due to a Cabin Altitude/Pressurization warning passing through FL260. During the descent it was discovered that the wrong altitude had been set in the Pressurization Control Panel.