ZIP 78666 vs ZIP 78155

This side-by-side compares ZIP 78666 (San Marcos, TX) and ZIP 78155 (Seguin, TX) using the same Census ACS 5-Year table fields for both — no averages swapped in, no national proxies. ZIP 78666 has a population of 63,836 at 140 people per square mile, while ZIP 78155 has 45,341 at 49 per square mile. That difference in population size and density alone reshapes how every other metric should be interpreted — a higher-income ZIP with 1,200 residents behaves very differently from one with 45,000.

On income and education, ZIP 78666 reports a median household income of $54,737 against $71,039 in ZIP 78155, with per-capita income of $29,465 vs $36,571. The share of adults holding a bachelor's degree or higher is 35.7% in 78666 and 21.7% in 78155. Poverty rate reads 23.8% vs 16.9%, and unemployment 5.2% vs 3.9% — these four fields alone drive most of the difference in the scorecard grades you will see for each ZIP.

Housing separates these two ZIPs further: median home value sits at $306,700 in 78666 versus $266,700 in 78155, with median rent of $1,319 and $1,198 per month respectively. Homeownership rate is 38.1% vs 72.5%. When reading the comparison table below, focus on paired metrics rather than single winners — a ZIP with lower home values and lower income is not strictly "worse" if rent-to-income ratios and commute times land in the same zone. Every value is pulled from the exact same ACS table so the two columns are genuinely comparable.