On December 21, 1620, the first landing party arrived at the site of Plymouth. Plans to build houses, however, were delayed by bad weather until December 23. As the building progressed, 20 men always remained ashore for security purposes while the rest of the work crews returned each night to the "Mayflower". Women, children, and the infirm remained on board the "Mayflower", and many had not left the ship for six months. The first structure was a common house of wattle and daub, and it took two weeks to complete in the harsh New England winter. In the following weeks, the rest of the settlement slowly took shape. The living and working structures were built on the relatively flat top of Cole's Hill, and a wooden platform was constructed atop nearby Fort Hill to support the cannon that would defend the settlement.