I've been an ideal tenant for seven years, and to thank me, my lanlord jacked the rent up seventy-five dollars in less than two years. Is this legal?

Unfortunately, yes.

In most areas a landlord can raise the rent as much as they like - as long as the period of the last lease agreement has been fulfilled.

To be sure, though, if you'll send me a copy of your lease, along with
1. What state you're in, and
2. a copy of your last rent change notice
I'd be happy to take a look at it.

Contact your town clerk to see if there is a rent control ordinance. If so then your landlord is limited in the amount that the rent can be increased. If not then unfortunately the landlord can increase the rent as much as he wants at the beginning of each new lease term.

If you're not in a rent control district, your landlord can increase the rent in accord with the lease.

Tenant rights vary depending on jurisdiction, but absent any rent control, it is legal to raise rent.