By the time a lot of higher education institutions were being founded in most other regions of the country, the most popular form had moved on to what became modern research universities, as opposed to LACs.
In fact here is a quick (Wikipedia based, so accept some errors) accounting of the founding dates of the top 20 on the US News list:
1: 1793
2: 1821
3: 1864
4: 1845
t-5: 1794, 1887
7: 1870
t-8: 1802, 1866, 1946, 1954
t-12: 1861, 1955
t-14: 1793, 1837, 1839, 1871, 1889
t-19: 1749, 1800, 1846
The only three in the 20th Century are two of the Claremont Colleges (CMC and Mudd), and the Air Force Academy. In fact even a lot of the later ones in the 19th Century are specifically women’s colleges, which trailed in founding a bit.
You can actually see this too if you look at this map. It is a couple years out of date now, but still gives you the idea:
https://www.usnews.com/education/best-colleges/articles/where-to-find-the-us-news-best-colleges
Compared to the blue dots (T50 National Universities), the red dots (T50 LACs) are relatively concentrated toward the Northeast. There is a cluster down in Southern California, and Whitman (1859) and Colorado College (1874) also in the west. But really you are mostly looking at a map of where people were founding a lot of colleges between the 1790s and 1870s or so, after which the modern university form mostly took over.