A wind resistant modular ISO building includes a first cargo container, a second cargo container, and a mounting system. The first and second cargo containers are joined to each other by attaching adjacent lengthwise frame rails. Most of an inner lengthwise side wall of the first and second cargo containers is removed. The first and second cargo containers are also joined to each other by attaching a plurality of vertical channels of upper portions of the lengthwise side walls. A plurality of horizontal channels are attached to the plurality of vertical channels. At least two moment frames are attached to an inside of the first and second cargo containers. The end door of the first and second cargo containers are replaced with an end panel. Preferably, at least one door entrance and window system is formed in at least one of the lengthwise side walls.