Who was raptured when Christ rose from the dead?
When Christ rose from the dead, the graves of many sleeping saints, including the Old Patriarchs who had been held captive in death, were opened, and their bodies came out of the graves and went into the holy city.
Scripture teaches that when Jesus died, the veil of the temple was torn, the earth quaked, the rocks split, and the graves of many sleeping saints were opened. Matthew records that after Jesus' resurrection, these bodies of the saints came out of their graves and appeared to many in the holy city. This was the rapture of the Old Patriarchs, those who had been held bound in death in the lower parts of the earth, waiting for the price of sin to be paid before they could be set free.
Jesus, having descended first into the lower parts of the earth, went and preached to the spirits in prison, those who had been disobedient in the days of Noah and others bound by death. Having paid the debt of sin, He was able to loose these captives, pouring out the Holy Spirit upon them so they could overcome death through the Spirit of life. Among those released were the Old Patriarchs listed in Hebrews 11, whose faith could not be completed without the rest of the Body of Christ joining them later.
Because Jesus used the keys of hell and of death that He obtained through His resurrection, He released these captives, and they emerged from the earth not as isolated individuals but as part of a Body with Christ as the Head, the first of many members. Scripture refers to them afterward as a cloud of witnesses and as the spirits of just men made perfect, now dwelling in heavenly places.
The scriptures
Jesus, when he had cried again with a loud voice, yielded up the ghost. And, behold, the veil of the temple was rent in twain from the top to the bottom; and the earth did quake, and the rocks rent; And the graves were opened; and many bodies of the saints which slept arose, And came out of the graves after his resurrection, and went into the holy city, and appeared unto many.
Therefore prophesy and say unto them, Thus saith the Lord GOD; Behold, O my people, I will open your graves, and cause you to come up out of your graves, and bring you into the land of Israel. And ye shall know that I am the LORD, when I have opened your graves, O my people, and brought you up out of your graves, And shall put my spirit in you, and ye shall live, and I shall place you in your own land: then shall ye know that I the LORD have spoken it, and performed it, saith the LORD.
(Now that he ascended, what is it but that he also descended first into the lower parts of the earth? He that descended is the same also that ascended up far above all heavens, that he might fill all things.)
For Christ also hath once suffered for sins, the just for the unjust, that he might bring us to God, being put to death in the flesh, but quickened by the Spirit: By which also he went and preached unto the spirits in prison; Which sometime were disobedient, when once the longsuffering of God waited in the days of Noah, while the ark was a preparing, wherein few, that is, eight souls were saved by water.
Wherefore seeing we also are compassed about with so great a cloud of witnesses, let us lay aside every weight, and the sin which doth so easily beset us, and let us run with patience the race that is set before us,
To the general assembly and church of the firstborn, which are written in heaven, and to God the Judge of all, and to the spirits of just men made perfect,
From the books
This answer is drawn from these passages in the Mary Banks Faith Library.