Mark McGwire had the highest on-base percentage by a first baseman in 1998, with an on-base percentage of .470.

Interpreted as:

highest obp with a minimum of 3.1 PA per team game in 1998 1st baseman

	NAME	OBP	SEASON	TM	G	AB	R	H	2B	3B	HR	RBI	BB	HBP	SO	SB	CS	PA	TB	XBH	SH	SF	IBB	GIDP	AVG	SLG	OPS	WRC	WRAA	WOBA	WRC+	BRAA
1	Mark McGwire M. McGwire	.470	1998	STL	155	509	130	152	21	0	70	147	162	6	155	1	0	681	383	91	0	4	28	8	.299	.752	1.222	176	91.7	.492	205	90.7
2	John Olerud J. Olerud	.447	1998	NYM	160	557	91	197	36	4	22	93	96	4	73	2	2	665	307	62	1	7	11	15	.354	.551	.998	137	54.6	.430	167	56.1
3	Jeff Bagwell J. Bagwell	.424	1998	HOU	147	540	124	164	33	1	34	111	109	7	90	19	7	661	301	68	0	5	8	14	.304	.557	.981	131	49.3	.421	163	52.4
4	Jim Thome J. Thome	.413	1998	CLE	123	440	89	129	34	2	30	85	89	4	141	1	0	537	257	66	0	4	8	7	.293	.584	.997	107	40.8	.422	152	36.3
5	Mo Vaughn M. Vaughn	.402	1998	BOS	154	609	107	205	31	2	40	115	61	8	144	0	0	681	360	73	0	3	13	13	.337	.591	.993	135	50.9	.421	151	45.2
6	Mark Grace M. Grace	.401	1998	CHC	158	595	92	184	39	3	17	89	93	3	56	4	7	698	280	59	0	7	8	17	.309	.471	.872	115	29	.381	130	26.2
7	Andres Galarraga A. Galarraga	.397	1998	ATL	153	555	103	169	27	1	44	121	63	25	146	7	6	648	330	72	0	5	11	8	.305	.595	.991	127	47.2	.418	156	46.2
8	Carlos Delgado C. Delgado	.385	1998	TOR	142	530	94	155	43	1	38	115	73	11	139	3	0	620	314	82	0	6	13	8	.292	.592	.978	117	40.3	.409	146	36.7
9	Will Clark W. Clark	.384	1998	TEX	149	554	98	169	41	1	23	102	72	3	97	1	0	636	281	65	0	7	5	15	.305	.507	.891	107	28.3	.385	126	21.4
10	Jason Giambi J. Giambi	.384	1998	OAK	153	562	92	166	28	0	27	110	81	5	102	2	2	657	275	55	0	9	7	16	.295	.489	.873	107	25.5	.378	126	22.4
11	Todd Helton T. Helton	.380	1998	COL	152	530	78	167	37	1	25	97	53	6	54	3	3	595	281	63	1	5	5	15	.315	.530	.911	103	29.7	.391	114	10.4
12	Rafael Palmeiro R. Palmeiro	.379	1998	BAL	162	619	98	183	36	1	43	121	79	7	91	11	7	709	350	80	0	4	8	14	.296	.565	.945	129	41.5	.401	144	40
13	Fred McGriff F. McGriff	.371	1998	TBD	151	564	73	160	33	0	19	81	79	2	118	7	2	649	250	52	0	4	9	14	.284	.443	.815	94	13.5	.356	111	8.9
14	David Segui D. Segui	.359	1998	SEA	143	522	79	159	36	1	19	84	49	0	80	3	1	580	254	56	0	9	4	12	.305	.487	.845	88	15.7	.364	116	12.3
15	Tony Clark T. Clark	.358	1998	DET	157	602	84	175	37	0	34	103	63	3	128	3	3	673	314	71	0	5	5	16	.291	.522	.880	109	25.6	.377	124	20.8
16	Tino Martinez T. Martinez	.355	1998	NYY	142	531	92	149	33	1	28	123	61	6	83	2	1	608	268	62	0	10	3	18	.281	.505	.860	94	19.1	.369	122	17
17	Eric Karros E. Karros	.355	1998	LAD	139	507	59	150	20	1	23	87	47	3	93	7	2	564	241	44	0	7	1	7	.296	.475	.830	84	13.8	.361	124	17.2
18	Darin Erstad D. Erstad	.353	1998	ANA	133	537	84	159	39	3	19	82	43	6	77	20	6	590	261	61	1	3	7	2	.296	.486	.839	88	14.6	.361	114	11.1
19	Hal Morris H. Morris	.350	1998	KCR	127	472	50	146	27	2	1	40	32	1	52	1	0	516	180	30	4	7	6	15	.309	.381	.731	60	-4.3	.321	87	-8.6
20	Travis Lee T. Lee	.346	1998	ARI	146	562	71	151	20	2	22	72	67	0	123	8	1	630	241	44	0	1	5	13	.269	.429	.775	83	4.8	.340	102	1.5
21	Kevin Young K. Young	.328	1998	PIT	159	592	88	160	40	2	27	108	44	11	127	15	7	656	285	69	0	9	1	20	.270	.481	.809	91	9.3	.348	108	6.7
22	Brad Fullmer B. Fullmer	.327	1998	MON	140	505	58	138	44	2	13	73	39	2	70	6	6	547	225	59	0	1	4	12	.273	.446	.773	69	1.7	.335	100	0.2
23	Rico Brogna R. Brogna	.319	1998	PHI	153	565	77	150	36	3	20	104	49	0	125	7	7	624	252	59	0	10	8	12	.265	.446	.765	75	-2.6	.326	94	-5.1
24	Jeff King J. King	.319	1998	KCR	131	486	83	128	17	1	24	93	42	2	73	10	2	540	219	42	0	10	1	10	.263	.451	.769	67	0.4	.332	94	-4.1
25	Derrek Lee D. Lee	.318	1998	FLA	141	454	62	106	29	1	17	74	47	10	120	5	2	513	188	47	0	2	1	12	.233	.414	.732	60	-3.6	.323	96	-2.5