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ABSTRACT  This paper focuses on a comparison of the space densities of Fanaroff–Riley type I (FR I) and FR II sources at different epochs, with a particular focus on FR I sources.  First, we present the concluding steps in constructing the Combined NVSS–FIRST Galaxies (CoNFIG) catalogue, including new Very Large Array observations, optical identifications and redshift estimates. The final catalogue consists of 859 sources over four samples (CoNFIG‐1, ‐2, ‐3 and ‐4 with flux density limits of   S  1.4 GHz  = 1.3, 0.8, 0.2 and 0.05 Jy, respectively). It is 95.7 per cent complete in radio morphology classification and 74.3 per cent of the sources have redshift data.  Combining CoNFIG with complementary samples, the distribution and evolution of FR I and FR II sources are investigated. We find that FR I sources undergo mild evolution and that, at the same radio luminosity, FR I and FR II sources show similar space density enhancements in various redshift ranges, possibly implying a common evolution.

The Combined NVSS–FIRST Galaxies (CoNFIG) sample – II. Comparison of space densities in the Fanaroff–Riley dichotomy