I see references here occasionally to "Four-year colleges" - would those have different course loads in early years than colleges that provide both 2 and 4 year degrees?
 The reference to four-year colleges has typically been to distinguish between institutions which students attend when earning Bachelor's degrees, and two-year colleges such as a technical college, community college, or junior college where the degrees granted are typically Associate degrees. 
A four-year college is one from which a Bachelor's degree can be obtained; A Bachelor's degree is typically considered a four-year degree. 
Four-year colleges may also include schools which offer advanced degree programs such as Masters, Ed.D., and Ph.D.  Some may also include medical schools offering MD.
At some 4-year colleges, students do not declare majors until completion of the second year (or after earning the number of credits equivalent to having completed second year, through programs/services available such as dual enrollment and transfer credit).  At these colleges, the first 2 years are typically dedicated to liberal arts and/or gen ed requirements.  The final two years are dedicated to classes in one's declared major area.
Some four-year colleges offer accelerated Summer courses and/or Winter break courses, allowing a Bachelor's degree to be completed in 3 years.  Some 4-year colleges may also offer Associates degrees.  These are examples of the melding occurring in education.  Dual-enrollment is another example of rather recent changes which impact the amount of time spent in college. These changes may make the reference to four-year colleges somewhat dated or obsolete.