Traditionally, Matthew was viewed as the first Gospel, hence its location first in the New Testament canon.
That said, beginning with Schleiermacher in the early 1800s, the idea that Mark was actually the first began to take hold.
The Gospel of Luke was written by the same author as the Acts of the Apostles, who refers to Luke as the 'former account' of 'all that Jesus began to do and teach' (Acts 1:1).
The destiny ('Theophilus'), style, and vocabulary of the two books betray a common author. The significance of Gallio's judgement in Acts -17 may be seen as setting precedent to legitimize Christian teaching under the umbrella of the tolerance extended to Judaism. The prominence and authority of the Sadducees in Acts reflects a pre-70 date, before the collapse of their political cooperation with Rome. The relatively sympathetic attitude in Acts to Pharisees (unlike that found even in Luke's Gospel) does not fit well with in the period of Pharisaic revival that led up to the council at Jamnia.
Famed exegete Daniel Wallace goes into detail on the so-called Synoptic Problem, asking how it is that three Gospel writers could include so much that is so similar, in even the same order.
While he does not deny inspiration by the Holy Spirit, he shows how the complete agreement would not really fit with three men independently relating the same facts, without some form of collaboration or borrowing.
‘Synoptic’ means a ‘with-viewing’, as these Gospels view many of the same events together.(Although even fair-minded biblical critics would have to agree that higher criticism’s 200-year failure to prove its case by default strengthens the conservative Christian view as to biblical reliability.) In this sense, the critics who continue to advance discredited theories conform to the warnings of Chauncey Sanders, associate professor of military history, The Air University, Maxwell Air Force Base, Montgomery, Alabama.In his An Introduction to Research In English Literary History, he warns literary critics to be certain they are also careful to examine the evidence against their case: …he must be as careful to collect evidence against his theory as for it.While the Synoptic Question is not entirely necessary to answer, and, as there is limited information to go on, all of the questions will never be answered certainly, yet the Synoptic Question is a legitimate one to ask and has believing, conservative answers.The first mainstream, establishment viewpoint of liberal scholarship from the late-1800’s was the priority of Mark, that Matthew and Luke derived their information from Mark, it being the simplest Gospel.