In this research work, a total of nine thousand (9,000) numbers of 6 inches (150 mm)-thick Sandcrete masonry blocks and another total of nine thousand (9,000) numbers of 9 inches (225 mm)-thick Sandcrete masonry blocks were collected as Testsamples from three hundred (300) Sandcrete block-making factories, which are randomly sited in thirty (30) rapidly developing towns/localities located within three (3) highly-populated and state-capital metropolitan-cities-i.e. 'Lagos', 'Ibadan' and 'Abeokuta' in South-Western Nigeria. Thus, from the cumulative total number of eighteen thousand (18,000) Sandcrete block testsamples, each of the thirty (30) numbers of ' 6 inch-thick block test-samples' and each of the thirty (30) numbers of ' 9 inch-thick block test-samples' which were collected from each of the ten ( 10) Block-making factories per town/locality was subjected to two (2) critical quality-evaluation tests-i.e. Compressive-strength () block f test [using a compression-testing machine] and Water absorption coefficient () AC W test [in accordance with standard established procedures and then, the mean values were computed and adopted as the representative/characteristic data for each Block-making factory. Consequently, the obtained results/data were then comparatively analysed using the Standards Organization of Nigeria 'SON' NIS 87: 2007 standard specified (recommended) values to empirically evaluate the Block-making/production quality of each of town/locality per city and of each city. Amongst other things, the comparative analysis of the obtained results/data showed that: while all (100%) of the tested Sandcrete masonry blocks produced in Lagos city and Ibadan city are classified as substandard-having failed to meet (fulfil) the NIS 87: 2007 standard requirements; just 30% of the 6"-thick Sandcrete masonry blocks, and as much as 50% of the 9"-thick Sandcrete masonry blocks produced in Abeokuta city are classified as standard-having successfully met (satisfied) the NIS 87: 2007 Standard requirements-thus, making them the most ideal for construction purposes.