My very first job was in a bike shop that sold Trek, in the early 90s. When I started, they were offering cromoly bikes with lugged construction (900 series) and bikes with bonded aluminum frames, and alu/carbon bonded frames all MUSA, and American made full-carbon ('OCLV). They also had the 800 series and some lower cost steel road bikes and kids bikes made in Taiwan. By the time I left that job a few years later they had moved all cromoly and aluminum frame production to Taiwan, and changed to TIG welding across the board.
A few years later they started getting entry level carbon frames made in Asia, with the higher end stuff still American. I believe they sent the higher end carbon production incrementally to Asia over the 00s and 10s. All is Asian now.