Alan> You might have better luck asking on a RHEL or CentOS list. In Alan> the repos I have enabled, I only see 1.15 is available
That's correct, and it's an embarrassment for them. Sadly the EPEL people don't package a newer version either. Maybe one from our lest could try to work with them on that. In my work this causes real problems: I release a huge simulation framework by building some 20 RPMs, and they need a newer GSL than 1.15. At first I made my own packages, but then they got in the way of other packages on Red Hat 7, so I had to create a differently named package (I called it gsl2_diorama, since our framework is called diorama) that installs in a different area (a bit like how Red Hat packages newer versions of the root C++ libraries). A lot of work to get that going, although it's made a bit easier by the careful use of autotools and of things like pkg-config and gsl-config.