"Había muerto mucha gente en ese lugar."
Translation:A lot of people had died in that place.
I thought others might also want to know some generalizations about word order so here's a link that may be helpful. Emphasis appears to the best fit.
"la gente," though it refers to many people, its a singular noun. You can think of it as "the crowd" or "a group of people." Notice how in English you'd have (I;m using present perfect here to indicate the difference) "Many people have died here" vs "a large crowd/group of people has died here" (I know it sounds a bit odd, but jsut trying to illustrate this)
Había is the general 1st- and 3rd-person singular imperfect tense of the helping verb haber, so it's mainly used in forming the past perfect tense. This conjugation form is usually translated as "I had", "he had", "she had", "it had", or "you had" (usted form).
The main verb in this sentence is morir - to die. It's an intransitive verb, so it doesn't take an object, so the only person mentioned here - mucha gente - must be the subject. It's the people who had died, not she.