In this dissertation, I examine the nature of object marking in American Sign Language (ASL). I investigate object marking by means of directionality (the movement of the verb towards a certain location in signing space) and by means of handling classifiers (certain handshapes accompanying the verb). I propose that object marking in ASL is licensed by two-place semantic operators. Directionality introduces a semantic variable to be bound. This variable is bound through forming a restriction based on where the object is located. I label the operator that binds the directionality variable as a Locative Operator (LocOP). A handling classifier handshape introduces a handshape variable. This variable is bound through forming a restriction based on the descriptive content of the object. I label the operator that binds the handshape variable as a Size and Shape Operator (SSOP). I support my semantic proposal by results from four experiments: gapping, wh-type, wh-clefts and sluices. These experiments show that there is really a variable and it cannot be deleted (gapping), that there is a preference for a restricting object to be d-linked and presuppositional (wh-type), and that specificity does not play a role in licensing object marking (sluicing). Based on results from a word order experiment, I propose that the operators may be located at the IP/TP or CP domains. When they are located at the IP/TP domain, the projection that hosts the operators is labeled a Quantificational/Presuppositional Phrase (Quant/PresupP). The restricting object may overtly move to the specifier position of this projection to yield the SOV order. Results of a negation experiment show that this projection needs to be higher than sentential negation but still within the IP/TP domain when the order is SOV. The word order results also reveal that there needs to be an ordering restriction for base-generated and derived orders of the Direct and Indirect Objects in object-marked sentences. The Direct Object needs to be higher than the Indirect Object in base- generated position whereas, when there is movement, the Indirect Object needs to move to a higher projection than the one that the Direct Object moves. Lastly, I show how object marking in ASL is different than both agreement and clitic-doubling in spoken languages. ASL seems to be immune to a structural diagnostic offered to differentiate between agreement and clitic-doubling. Evidence to how ASL object marking differs from agreement and clitic-doubling is offered from structural environments where the relation between object marking on the verb and the restricting object is intervened by a clausal boundary created by embedding or one created by an if-clause. This work contributes to discussions of how one can account for argument marking on a verb within the linguistic system as well as adding to our knowledge of the descriptive study of ASL. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]