Linguists have debated whether complex prepositions deserve a constituent status, but none have proposed a dynamic model that can both predict what construal a given pattern imposes and account for the emergence of non-spatial readings. This paper reframes the debate on constituency as a justification of the constructional status of complex prepositional patterns from a historical perspective. It focuses on the Prep NP IL of NP lm construction, which denotes a relation of internal location between a located entity (a trajector) and a reference entity (a landmark). Four subschemas of the Internal Location construction are examined: MIDDLE cxn (in the middle of), CENTER cxn (in/at the center of), HEART cxn (in/at the heart of), and MIDST cxn (in the midst of). All occurrences are extracted from the COHA, along with their co-occurring landmark NPs. Using vocabulary growth curves, all patterns are shown to be productive over the whole period covered by the corpus, although at different levels. Using word2vec, a semantic vector space with the landmark collocates of each pattern is made. Curves indexed on association scores are plotted to see how densely semantic areas have been populated across four consecutive periods: 1810s-1860s, 1870s-1910s, 1920s-1970s, and 1980s-2000s. Two divisions of labor have emerged. MIDST cxn and HEART cxn are in complementary distribution and operate mostly at the level of abstract locations whereas MIDDLE cxn and CENTER cxn are in parallel distribution and operate at the level of concrete locations.