a fort in the backyard, Grandpa comes forward to help. But they can't do it alone--they get help from the six simple machines: lever, pulley, inclined plane, wheel and axle, screw, and wedge. Told in cumulative rhyme, similar to The House That Jack Built, readers follow the building process to completion and discover the surprise reason it was built. This fictional story with rhyming text includes a 4-page For Creative Minds section in the back of the book and a 34-page cross-curricular Teaching Activity Guide online. The Fort on Fourth Street is vetted by experts and designed to encourage parental engagement. Its extensive back matter helps teachers with time-saving lesson ideas, provides extensions for science, math, and social studies units, and uses inquiry-based learning to help build critical thinking skills in young readers. The Spanish translation supports ELL and dual-language programs. The interactive ebook reads aloud in both English and Spanish with word highlighting and audio speed control to promote oral language skills, fluency, pronunciation, text engagement, and reading comprehension.