This 1885 map shows what would become the northern part of Columbia Heights. At the time, it was still referred to as part of Mt. Pleasant. The arrow at left points to north. Also, some street names were renamed, so Howard became Newton and Sheridan became Monroe. Click on it for a larger version.
Source: Library of Congress
And “16th Street Extension” on the map became Mt. Pleasant Street + 17th St. The modern 16th St. doesn’t appear, except at the very top where “14th St” (now Ogden St) continues north.